81560257 has 2 divisors, whose sum is σ = 81560258. Its totient is φ = 81560256.

The previous prime is 81560249. The next prime is 81560261. The reversal of 81560257 is 75206518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81558961 + 1296 = 9031^2 + 36^2 .

It is a cyclic number.

It is not a de Polignac number, because 81560257 - 2³ = 81560249 is a prime.

It is not a weakly prime, because it can be changed into another prime (81560657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40780128 + 40780129.

It is an arithmetic number, because the mean of its divisors is an integer number (40780129).

Almost surely, 2^81560257 is an apocalyptic number.

It is an amenable number.

81560257 is a deficient number, since it is larger than the sum of its proper divisors (1).

81560257 is an equidigital number, since it uses as much as digits as its factorization.

81560257 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16800, while the sum is 34.

The square root of 81560257 is about 9031.0717525662. The cubic root of 81560257 is about 433.6701483282.

The spelling of 81560257 in words is "eighty-one million, five hundred sixty thousand, two hundred fifty-seven".