81776531 has 2 divisors, whose sum is σ = 81776532. Its totient is φ = 81776530.

The previous prime is 81776507. The next prime is 81776567. The reversal of 81776531 is 13567718.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81776531 - 2¹⁸ = 81514387 is a prime.

It is a super-2 number, since 2×81776531² = 13374802044787922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (81776501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40888265 + 40888266.

It is an arithmetic number, because the mean of its divisors is an integer number (40888266).

Almost surely, 2^81776531 is an apocalyptic number.

81776531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81776531 is an equidigital number, since it uses as much as digits as its factorization.

81776531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 35280, while the sum is 38.

The square root of 81776531 is about 9043.0377086464. The cubic root of 81776531 is about 434.0531322323.

The spelling of 81776531 in words is "eighty-one million, seven hundred seventy-six thousand, five hundred thirty-one".