81256672457 has 2 divisors, whose sum is σ = 81256672458. Its totient is φ = 81256672456.

The previous prime is 81256672429. The next prime is 81256672481. The reversal of 81256672457 is 75427665218.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 58963494976 + 22293177481 = 242824^2 + 149309^2 .

It is a cyclic number.

It is not a de Polignac number, because 81256672457 - 2¹⁴ = 81256656073 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81256672399 and 81256672408.

It is not a weakly prime, because it can be changed into another prime (81256678457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40628336228 + 40628336229.

It is an arithmetic number, because the mean of its divisors is an integer number (40628336229).

Almost surely, 2^81256672457 is an apocalyptic number.

It is an amenable number.

81256672457 is a deficient number, since it is larger than the sum of its proper divisors (1).

81256672457 is an equidigital number, since it uses as much as digits as its factorization.

81256672457 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5644800, while the sum is 53.

The spelling of 81256672457 in words is "eighty-one billion, two hundred fifty-six million, six hundred seventy-two thousand, four hundred fifty-seven".