31221010021 has 2 divisors, whose sum is σ = 31221010022. Its totient is φ = 31221010020.

The previous prime is 31221010013. The next prime is 31221010039. The reversal of 31221010021 is 12001012213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 28321187521 + 2899822500 = 168289^2 + 53850^2 .

It is a cyclic number.

It is not a de Polignac number, because 31221010021 - 2³ = 31221010013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31221009983 and 31221010010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31221010321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15610505010 + 15610505011.

It is an arithmetic number, because the mean of its divisors is an integer number (15610505011).

Almost surely, 2^31221010021 is an apocalyptic number.

It is an amenable number.

31221010021 is a deficient number, since it is larger than the sum of its proper divisors (1).

31221010021 is an equidigital number, since it uses as much as digits as its factorization.

31221010021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24, while the sum is 13.

Adding to 31221010021 its reverse (12001012213), we get a palindrome (43222022234).

The spelling of 31221010021 in words is "thirty-one billion, two hundred twenty-one million, ten thousand, twenty-one".