81930857731 has 4 divisors (see below), whose sum is σ = 82388572200. Its totient is φ = 81473143264.

The previous prime is 81930857707. The next prime is 81930857819. The reversal of 81930857731 is 13775803918.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81930857731 is a prime.

It is a super-2 number, since 2×81930857731² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81930857131) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 228856966 + ... + 228857323.

It is an arithmetic number, because the mean of its divisors is an integer number (20597143050).

Almost surely, 2^81930857731 is an apocalyptic number.

81930857731 is a deficient number, since it is larger than the sum of its proper divisors (457714469).

81930857731 is a wasteful number, since it uses less digits than its factorization.

81930857731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 457714468.

The product of its (nonzero) digits is 1270080, while the sum is 52.

The spelling of 81930857731 in words is "eighty-one billion, nine hundred thirty million, eight hundred fifty-seven thousand, seven hundred thirty-one".