644037644 has 6 divisors (see below), whose sum is σ = 1127065884. Its totient is φ = 322018820.

The previous prime is 644037629. The next prime is 644037649. The reversal of 644037644 is 446730446.

It is a junction number, because it is equal to n+sod(n) for n = 644037598 and 644037607.

It is not an unprimeable number, because it can be changed into a prime (644037649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80504702 + ... + 80504709.

It is an arithmetic number, because the mean of its divisors is an integer number (187844314).

Almost surely, 2^644037644 is an apocalyptic number.

It is an amenable number.

644037644 is a deficient number, since it is larger than the sum of its proper divisors (483028240).

644037644 is a wasteful number, since it uses less digits than its factorization.

644037644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161009415 (or 161009413 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 38.

The square root of 644037644 is about 25377.8967607641. The cubic root of 644037644 is about 863.5823366401.

The spelling of 644037644 in words is "six hundred forty-four million, thirty-seven thousand, six hundred forty-four".