81057731 has 2 divisors, whose sum is σ = 81057732. Its totient is φ = 81057730.

The previous prime is 81057719. The next prime is 81057733. The reversal of 81057731 is 13775018.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81057731 - 2¹⁸ = 80795587 is a prime.

It is a super-2 number, since 2×81057731² = 13140711509736722, which contains 22 as substring.

Together with 81057733, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_4727642 and since 81057731 and 4727642 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (81057733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40528865 + 40528866.

It is an arithmetic number, because the mean of its divisors is an integer number (40528866).

Almost surely, 2^81057731 is an apocalyptic number.

81057731 is a deficient number, since it is larger than the sum of its proper divisors (1).

81057731 is an equidigital number, since it uses as much as digits as its factorization.

81057731 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5880, while the sum is 32.

The square root of 81057731 is about 9003.2067065019. The cubic root of 81057731 is about 432.7776399028. Note that the first 3 decimals are identical.

The spelling of 81057731 in words is "eighty-one million, fifty-seven thousand, seven hundred thirty-one".