644433984 has 42 divisors (see below), whose sum is σ = 1847155310. Its totient is φ = 214811136.

The previous prime is 644433973. The next prime is 644433989. The reversal of 644433984 is 489334446.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 638673984 + 5760000 = 25272^2 + 2400^2 .

It is a super-2 number, since 2×644433984² = 830590319468224512, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (644433989) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 558829 + ... + 559980.

Almost surely, 2^644433984 is an apocalyptic number.

644433984 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

644433984 is an abundant number, since it is smaller than the sum of its proper divisors (1202721326).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644433984 is a wasteful number, since it uses less digits than its factorization.

644433984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1118827 (or 1118814 counting only the distinct ones).

The product of its digits is 995328, while the sum is 45.

The square root of 644433984 is about 25385.7043234967. The cubic root of 644433984 is about 863.7594494943.

The spelling of 644433984 in words is "six hundred forty-four million, four hundred thirty-three thousand, nine hundred eighty-four".