644377973 has 2 divisors, whose sum is σ = 644377974. Its totient is φ = 644377972.

The previous prime is 644377961. The next prime is 644378011. The reversal of 644377973 is 379773446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 586511524 + 57866449 = 24218^2 + 7607^2 .

It is a cyclic number.

It is not a de Polignac number, because 644377973 - 2⁸ = 644377717 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644337973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322188986 + 322188987.

It is an arithmetic number, because the mean of its divisors is an integer number (322188987).

Almost surely, 2^644377973 is an apocalyptic number.

It is an amenable number.

644377973 is a deficient number, since it is larger than the sum of its proper divisors (1).

644377973 is an equidigital number, since it uses as much as digits as its factorization.

644377973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2667168, while the sum is 50.

The square root of 644377973 is about 25384.6010998794. The cubic root of 644377973 is about 863.7344242093.

It can be divided in two parts, 64437797 and 3, that multiplied together give a palindrome (193313391).

The spelling of 644377973 in words is "six hundred forty-four million, three hundred seventy-seven thousand, nine hundred seventy-three".