644237764 has 6 divisors (see below), whose sum is σ = 1127416094. Its totient is φ = 322118880.

The previous prime is 644237717. The next prime is 644237773. The reversal of 644237764 is 467732446.

It can be written as a sum of positive squares in only one way, i.e., 601230400 + 43007364 = 24520^2 + 6558^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 644237764.

It is an unprimeable number.

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, 80529717 + ... + 80529724.

Almost surely, 2^644237764 is an apocalyptic number.

It is an amenable number.

644237764 is a deficient number, since it is larger than the sum of its proper divisors (483178330).

644237764 is a wasteful number, since it uses less digits than its factorization.

644237764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161059445 (or 161059443 counting only the distinct ones).

The product of its digits is 677376, while the sum is 43.

The square root of 644237764 is about 25381.8392556568. The cubic root of 644237764 is about 863.6717735449.

The spelling of 644237764 in words is "six hundred forty-four million, two hundred thirty-seven thousand, seven hundred sixty-four".