31725490021 has 2 divisors, whose sum is σ = 31725490022. Its totient is φ = 31725490020.

The previous prime is 31725489973. The next prime is 31725490031. The reversal of 31725490021 is 12009452713.

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., 31724596996 + 893025 = 178114^2 + 945^2 .

It is an emirp because it is prime and its reverse (12009452713) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 31725490021 - 2⁷ = 31725489893 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31725490031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15862745010 + 15862745011.

It is an arithmetic number, because the mean of its divisors is an integer number (15862745011).

Almost surely, 2^31725490021 is an apocalyptic number.

It is an amenable number.

31725490021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31725490021 is an equidigital number, since it uses as much as digits as its factorization.

31725490021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15120, while the sum is 34.

The spelling of 31725490021 in words is "thirty-one billion, seven hundred twenty-five million, four hundred ninety thousand, twenty-one".