313121021821 has 2 divisors, whose sum is σ = 313121021822. Its totient is φ = 313121021820.

The previous prime is 313121021809. The next prime is 313121021831. The reversal of 313121021821 is 128120121313.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 309454113796 + 3666908025 = 556286^2 + 60555^2 .

It is a cyclic number.

It is not a de Polignac number, because 313121021821 - 2⁹ = 313121021309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (313121021831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 156560510910 + 156560510911.

It is an arithmetic number, because the mean of its divisors is an integer number (156560510911).

Almost surely, 2^313121021821 is an apocalyptic number.

It is an amenable number.

313121021821 is a deficient number, since it is larger than the sum of its proper divisors (1).

313121021821 is an equidigital number, since it uses as much as digits as its factorization.

313121021821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 25.

The spelling of 313121021821 in words is "three hundred thirteen billion, one hundred twenty-one million, twenty-one thousand, eight hundred twenty-one".