1320721931 has 2 divisors, whose sum is σ = 1320721932. Its totient is φ = 1320721930.

The previous prime is 1320721867. The next prime is 1320721933. The reversal of 1320721931 is 1391270231.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1320721931 - 2⁶ = 1320721867 is a prime.

It is a super-2 number, since 2×1320721931² = 3488612838048737522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 1320721933, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 1320721894 and 1320721903.

It is not a weakly prime, because it can be changed into another prime (1320721933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 660360965 + 660360966.

It is an arithmetic number, because the mean of its divisors is an integer number (660360966).

Almost surely, 2^1320721931 is an apocalyptic number.

1320721931 is a deficient number, since it is larger than the sum of its proper divisors (1).

1320721931 is an equidigital number, since it uses as much as digits as its factorization.

1320721931 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2268, while the sum is 29.

The square root of 1320721931 is about 36341.7381395002. The cubic root of 1320721931 is about 1097.1612564578.

The spelling of 1320721931 in words is "one billion, three hundred twenty million, seven hundred twenty-one thousand, nine hundred thirty-one".