81957643 has 8 divisors (see below), whose sum is σ = 83556576. Its totient is φ = 80371200.

The previous prime is 81957637. The next prime is 81957677. The reversal of 81957643 is 34675918.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81957643 is a prime.

It is a super-2 number, since 2×81957643² = 13434110492230898, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81957643.

It is not an unprimeable number, because it can be changed into a prime (81957443) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10713 + ... + 16693.

It is an arithmetic number, because the mean of its divisors is an integer number (10444572).

Almost surely, 2^81957643 is an apocalyptic number.

81957643 is a deficient number, since it is larger than the sum of its proper divisors (1598933).

81957643 is a wasteful number, since it uses less digits than its factorization.

81957643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6245.

The product of its digits is 181440, while the sum is 43.

The square root of 81957643 is about 9053.0460619617. The cubic root of 81957643 is about 434.3733311393.

The spelling of 81957643 in words is "eighty-one million, nine hundred fifty-seven thousand, six hundred forty-three".