1320631721 has 2 divisors, whose sum is σ = 1320631722. Its totient is φ = 1320631720.

The previous prime is 1320631699. The next prime is 1320631729. The reversal of 1320631721 is 1271360231.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1155252121 + 165379600 = 33989^2 + 12860^2 .

It is a cyclic number.

It is not a de Polignac number, because 1320631721 - 2¹⁰ = 1320630697 is a prime.

It is a super-2 number, since 2×1320631721² = 3488136285022843682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1320631729) 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, 660315860 + 660315861.

It is an arithmetic number, because the mean of its divisors is an integer number (660315861).

Almost surely, 2^1320631721 is an apocalyptic number.

It is an amenable number.

1320631721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1320631721 is an equidigital number, since it uses as much as digits as its factorization.

1320631721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 1320631721 is about 36340.4969833931. The cubic root of 1320631721 is about 1097.1362758851.

Adding to 1320631721 its reverse (1271360231), we get a palindrome (2591991952).

The spelling of 1320631721 in words is "one billion, three hundred twenty million, six hundred thirty-one thousand, seven hundred twenty-one".