646115511721 has 2 divisors, whose sum is σ = 646115511722. Its totient is φ = 646115511720.

The previous prime is 646115511637. The next prime is 646115511791. The reversal of 646115511721 is 127115511646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 542968554496 + 103146957225 = 736864^2 + 321165^2 .

It is a cyclic number.

It is not a de Polignac number, because 646115511721 - 2⁷ = 646115511593 is a prime.

It is not a weakly prime, because it can be changed into another prime (646115511791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323057755860 + 323057755861.

It is an arithmetic number, because the mean of its divisors is an integer number (323057755861).

Almost surely, 2^646115511721 is an apocalyptic number.

It is an amenable number.

646115511721 is a deficient number, since it is larger than the sum of its proper divisors (1).

646115511721 is an equidigital number, since it uses as much as digits as its factorization.

646115511721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 50400, while the sum is 40.

The spelling of 646115511721 in words is "six hundred forty-six billion, one hundred fifteen million, five hundred eleven thousand, seven hundred twenty-one".