Search a number
-
+
21111111 = 3772197
BaseRepresentation
bin101000010001…
…0000101000111
31110201120000000
41100202011013
520401023421
62032252343
7344304300
oct120420507
943646000
1021111111
1110a0a0aa
1270a10b3
1344b20a8
142b377a7
151cc0226
hex1422147

21111111 has 48 divisors (see below), whose sum is σ = 37018080. Its totient is φ = 12002256.

The previous prime is 21111073. The next prime is 21111113. The reversal of 21111111 is 11111112.

It is not a de Polignac number, because 21111111 - 213 = 21102919 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

21111111 is a modest number, since divided by 11111 gives 211 as remainder.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 21111093 and 21111102.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111113) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 107065 + ... + 107261.

It is an arithmetic number, because the mean of its divisors is an integer number (771210).

Almost surely, 221111111 is an apocalyptic number.

21111111 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21111111 is a deficient number, since it is larger than the sum of its proper divisors (15906969).

21111111 is an frugal number, since it uses more digits than its factorization.

21111111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232 (or 207 counting only the distinct ones).

The product of its digits is 2, while the sum is 9.

The square root of 21111111 is about 4594.6829052721. The cubic root of 21111111 is about 276.3781442434.

Adding to 21111111 its reverse (11111112), we get a palindrome (32222223).

Subtracting from 21111111 its reverse (11111112), we obtain a palindrome (9999999).

It can be divided in two parts, 2111111 and 1, that added together give a palindrome (2111112).

The spelling of 21111111 in words is "twenty-one million, one hundred eleven thousand, one hundred eleven".

Divisors: 1 3 7 9 21 27 49 63 81 147 189 197 243 441 567 591 729 1323 1379 1701 1773 2187 3969 4137 5103 5319 9653 11907 12411 15309 15957 28959 35721 37233 47871 86877 107163 111699 143613 260631 335097 430839 781893 1005291 2345679 3015873 7037037 21111111