644140751 has 2 divisors, whose sum is σ = 644140752. Its totient is φ = 644140750.

The previous prime is 644140741. The next prime is 644140771. The reversal of 644140751 is 157041446.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644140751 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644140711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322070375 + 322070376.

It is an arithmetic number, because the mean of its divisors is an integer number (322070376).

Almost surely, 2^644140751 is an apocalyptic number.

644140751 is a deficient number, since it is larger than the sum of its proper divisors (1).

644140751 is an equidigital number, since it uses as much as digits as its factorization.

644140751 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13440, while the sum is 32.

The square root of 644140751 is about 25379.9281125853. The cubic root of 644140751 is about 863.6284191600.

The spelling of 644140751 in words is "six hundred forty-four million, one hundred forty thousand, seven hundred fifty-one".