81520057 has 2 divisors, whose sum is σ = 81520058. Its totient is φ = 81520056.

The previous prime is 81520009. The next prime is 81520063. The reversal of 81520057 is 75002518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74235456 + 7284601 = 8616^2 + 2699^2 .

It is a cyclic number.

It is not a de Polignac number, because 81520057 - 2⁷ = 81519929 is a prime.

It is not a weakly prime, because it can be changed into another prime (81520757) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40760028 + 40760029.

It is an arithmetic number, because the mean of its divisors is an integer number (40760029).

Almost surely, 2^81520057 is an apocalyptic number.

It is an amenable number.

81520057 is a deficient number, since it is larger than the sum of its proper divisors (1).

81520057 is an equidigital number, since it uses as much as digits as its factorization.

81520057 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2800, while the sum is 28.

The square root of 81520057 is about 9028.8458287868. The cubic root of 81520057 is about 433.5988864757.

The spelling of 81520057 in words is "eighty-one million, five hundred twenty thousand, fifty-seven".