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81643431 = 3159717041
BaseRepresentation
bin1001101110111…
…00011110100111
312200121220201210
410313130132213
5131400042211
612033522503
72010646332
oct467343647
9180556653
1081643431
11420a3a11
1223413433
1313bb742c
14abb3619
15727a9a6
hex4ddc7a7

81643431 has 8 divisors (see below), whose sum is σ = 108932464. Its totient is φ = 54391680.

The previous prime is 81643427. The next prime is 81643459. The reversal of 81643431 is 13434618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81643431 - 22 = 81643427 is a prime.

It is a super-2 number, since 2×816434312 = 13331299650903522, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81643481) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3730 + ... + 13311.

It is an arithmetic number, because the mean of its divisors is an integer number (13616558).

Almost surely, 281643431 is an apocalyptic number.

81643431 is a deficient number, since it is larger than the sum of its proper divisors (27289033).

81643431 is a wasteful number, since it uses less digits than its factorization.

81643431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18641.

The product of its digits is 6912, while the sum is 30.

The square root of 81643431 is about 9035.6754589793. The cubic root of 81643431 is about 433.8175151460.

The spelling of 81643431 in words is "eighty-one million, six hundred forty-three thousand, four hundred thirty-one".

Divisors: 1 3 1597 4791 17041 51123 27214477 81643431