31646560721621 has 2 divisors, whose sum is σ = 31646560721622. Its totient is φ = 31646560721620.

The previous prime is 31646560721599. The next prime is 31646560721623. The reversal of 31646560721621 is 12612706564613.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15952595164900 + 15693965556721 = 3994070^2 + 3961561^2 .

It is a cyclic number.

It is not a de Polignac number, because 31646560721621 - 2¹⁴ = 31646560705237 is a prime.

Together with 31646560721623, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 31646560721621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31646560721623) 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, 15823280360810 + 15823280360811.

It is an arithmetic number, because the mean of its divisors is an integer number (15823280360811).

Almost surely, 2^{31646560721621} is an apocalyptic number.

It is an amenable number.

31646560721621 is a deficient number, since it is larger than the sum of its proper divisors (1).

31646560721621 is an equidigital number, since it uses as much as digits as its factorization.

31646560721621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2177280, while the sum is 50.

The spelling of 31646560721621 in words is "thirty-one trillion, six hundred forty-six billion, five hundred sixty million, seven hundred twenty-one thousand, six hundred twenty-one".