644398917131 has 2 divisors, whose sum is σ = 644398917132. Its totient is φ = 644398917130.

The previous prime is 644398917109. The next prime is 644398917143. The reversal of 644398917131 is 131719893446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644398917131 is a prime.

It is a super-2 number, since 2×644398917131² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644398917161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322199458565 + 322199458566.

It is an arithmetic number, because the mean of its divisors is an integer number (322199458566).

Almost surely, 2^644398917131 is an apocalyptic number.

644398917131 is a deficient number, since it is larger than the sum of its proper divisors (1).

644398917131 is an equidigital number, since it uses as much as digits as its factorization.

644398917131 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3919104, while the sum is 56.

The spelling of 644398917131 in words is "six hundred forty-four billion, three hundred ninety-eight million, nine hundred seventeen thousand, one hundred thirty-one".