81606457 has 2 divisors, whose sum is σ = 81606458. Its totient is φ = 81606456.

The previous prime is 81606431. The next prime is 81606479. The reversal of 81606457 is 75460618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 70073641 + 11532816 = 8371^2 + 3396^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81606457 is a prime.

It is a super-2 number, since 2×81606457² = 13319227648185698, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81606407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40803228 + 40803229.

It is an arithmetic number, because the mean of its divisors is an integer number (40803229).

Almost surely, 2^81606457 is an apocalyptic number.

It is an amenable number.

81606457 is a deficient number, since it is larger than the sum of its proper divisors (1).

81606457 is an equidigital number, since it uses as much as digits as its factorization.

81606457 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40320, while the sum is 37.

The square root of 81606457 is about 9033.6292263962. The cubic root of 81606457 is about 433.7520173647.

The spelling of 81606457 in words is "eighty-one million, six hundred six thousand, four hundred fifty-seven".