31221220813 has 2 divisors, whose sum is σ = 31221220814. Its totient is φ = 31221220812.

The previous prime is 31221220801. The next prime is 31221220841. The reversal of 31221220813 is 31802212213.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21041823364 + 10179397449 = 145058^2 + 100893^2 .

It is a cyclic number.

It is not a de Polignac number, because 31221220813 - 2¹⁷ = 31221089741 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31221220853) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15610610406 + 15610610407.

It is an arithmetic number, because the mean of its divisors is an integer number (15610610407).

Almost surely, 2^31221220813 is an apocalyptic number.

It is an amenable number.

31221220813 is a deficient number, since it is larger than the sum of its proper divisors (1).

31221220813 is an equidigital number, since it uses as much as digits as its factorization.

31221220813 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1152, while the sum is 25.

The spelling of 31221220813 in words is "thirty-one billion, two hundred twenty-one million, two hundred twenty thousand, eight hundred thirteen".