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18999981 = 33711131937
BaseRepresentation
bin100100001111…
…0101010101101
31022202022002000
41020132222231
514330444411
61515122513
7320332350
oct110365255
938668060
1018999981
11a7a7a70
126443439
133c231c0
142748297
151a04956
hex121eaad

18999981 has 128 divisors (see below), whose sum is σ = 40857600. Its totient is φ = 8398080.

The previous prime is 18999979. The next prime is 18999989.

18999981 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 18999981 - 21 = 18999979 is a prime.

It is a super-2 number, since 2×189999812 = 721998556000722, which contains 22 as substring.

Its product of digits (419904) is a multiple of the sum of its prime factors (96).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18999989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 513495 + ... + 513531.

It is an arithmetic number, because the mean of its divisors is an integer number (319200).

Almost surely, 218999981 is an apocalyptic number.

18999981 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18999981 is an abundant number, since it is smaller than the sum of its proper divisors (21857619).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18999981 is a wasteful number, since it uses less digits than its factorization.

18999981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96 (or 90 counting only the distinct ones).

The product of its digits is 419904, while the sum is 54.

The square root of 18999981 is about 4358.8967640907. The cubic root of 18999981 is about 266.8400759254.

It can be divided in two parts, 189 and 99981, that multiplied together give a square (18896409 = 43472).

The spelling of 18999981 in words is "eighteen million, nine hundred ninety-nine thousand, nine hundred eighty-one".

Divisors: 1 3 7 9 11 13 19 21 27 33 37 39 57 63 77 91 99 111 117 133 143 171 189 209 231 247 259 273 297 333 351 399 407 429 481 513 627 693 703 741 777 819 999 1001 1197 1221 1287 1443 1463 1729 1881 2079 2109 2223 2331 2457 2717 2849 3003 3367 3591 3663 3861 4329 4389 4921 5187 5291 5643 6327 6669 6993 7733 8151 8547 9009 9139 10101 10989 12987 13167 14763 15561 15873 18981 19019 23199 24453 25641 27027 27417 30303 37037 39501 44289 46683 47619 54131 57057 63973 69597 73359 76923 82251 90909 100529 111111 132867 142857 162393 171171 191919 208791 246753 301587 333333 487179 513513 575757 703703 904761 999999 1461537 1727271 2111109 2714283 6333327 18999981