81565704037 has 2 divisors, whose sum is σ = 81565704038. Its totient is φ = 81565704036.

The previous prime is 81565703951. The next prime is 81565704107. The reversal of 81565704037 is 73040756518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 81493691841 + 72012196 = 285471^2 + 8486^2 .

It is a cyclic number.

It is not a de Polignac number, because 81565704037 - 2³¹ = 79418220389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81565744037) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40782852018 + 40782852019.

It is an arithmetic number, because the mean of its divisors is an integer number (40782852019).

Almost surely, 2^81565704037 is an apocalyptic number.

It is an amenable number.

81565704037 is a deficient number, since it is larger than the sum of its proper divisors (1).

81565704037 is an equidigital number, since it uses as much as digits as its factorization.

81565704037 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 705600, while the sum is 46.

The spelling of 81565704037 in words is "eighty-one billion, five hundred sixty-five million, seven hundred four thousand, thirty-seven".