81511511737 has 2 divisors, whose sum is σ = 81511511738. Its totient is φ = 81511511736.

The previous prime is 81511511677. The next prime is 81511511759. The reversal of 81511511737 is 73711511518.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 80726447376 + 785064361 = 284124^2 + 28019^2 .

It is a cyclic number.

It is not a de Polignac number, because 81511511737 - 2²³ = 81503123129 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81511511737.

It is not a weakly prime, because it can be changed into another prime (81511311737) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40755755868 + 40755755869.

It is an arithmetic number, because the mean of its divisors is an integer number (40755755869).

Almost surely, 2^81511511737 is an apocalyptic number.

It is an amenable number.

81511511737 is a deficient number, since it is larger than the sum of its proper divisors (1).

81511511737 is an equidigital number, since it uses as much as digits as its factorization.

81511511737 is an evil number, because the sum of its binary digits is even.

The product of its digits is 29400, while the sum is 40.

The spelling of 81511511737 in words is "eighty-one billion, five hundred eleven million, five hundred eleven thousand, seven hundred thirty-seven".