81057681 has 24 divisors (see below), whose sum is σ = 124263360. Its totient is φ = 50805216.

The previous prime is 81057677. The next prime is 81057707. The reversal of 81057681 is 18675018.

81057681 is a `hidden beast` number, since 8 + 1 + 0 + 576 + 81 = 666.

It is not a de Polignac number, because 81057681 - 2² = 81057677 is a prime.

It is a super-2 number, since 2×81057681² = 13140695298195522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81057661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8895 + ... + 15531.

It is an arithmetic number, because the mean of its divisors is an integer number (5177640).

Almost surely, 2^81057681 is an apocalyptic number.

It is an amenable number.

81057681 is a deficient number, since it is larger than the sum of its proper divisors (43205679).

81057681 is a wasteful number, since it uses less digits than its factorization.

81057681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6725 (or 6722 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 36.

The square root of 81057681 is about 9003.2039297130. The cubic root of 81057681 is about 432.7775509173. Note that the first 3 decimals are identical.

The spelling of 81057681 in words is "eighty-one million, fifty-seven thousand, six hundred eighty-one".