31537816561 has 2 divisors, whose sum is σ = 31537816562. Its totient is φ = 31537816560.

The previous prime is 31537816549. The next prime is 31537816571. The reversal of 31537816561 is 16561873513.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 28983019536 + 2554797025 = 170244^2 + 50545^2 .

It is a cyclic number.

It is not a de Polignac number, because 31537816561 - 2⁷ = 31537816433 is a prime.

It is not a weakly prime, because it can be changed into another prime (31537816571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15768908280 + 15768908281.

It is an arithmetic number, because the mean of its divisors is an integer number (15768908281).

Almost surely, 2^31537816561 is an apocalyptic number.

It is an amenable number.

31537816561 is a deficient number, since it is larger than the sum of its proper divisors (1).

31537816561 is an equidigital number, since it uses as much as digits as its factorization.

31537816561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 453600, while the sum is 46.

The spelling of 31537816561 in words is "thirty-one billion, five hundred thirty-seven million, eight hundred sixteen thousand, five hundred sixty-one".