31578741721 has 2 divisors, whose sum is σ = 31578741722. Its totient is φ = 31578741720.

The previous prime is 31578741679. The next prime is 31578741737. The reversal of 31578741721 is 12714787513.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18019303696 + 13559438025 = 134236^2 + 116445^2 .

It is a cyclic number.

It is not a de Polignac number, because 31578741721 - 2³³ = 22988807129 is a prime.

It is not a weakly prime, because it can be changed into another prime (31578741791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15789370860 + 15789370861.

It is an arithmetic number, because the mean of its divisors is an integer number (15789370861).

Almost surely, 2^31578741721 is an apocalyptic number.

It is an amenable number.

31578741721 is a deficient number, since it is larger than the sum of its proper divisors (1).

31578741721 is an equidigital number, since it uses as much as digits as its factorization.

31578741721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 329280, while the sum is 46.

The spelling of 31578741721 in words is "thirty-one billion, five hundred seventy-eight million, seven hundred forty-one thousand, seven hundred twenty-one".