644781312 has 108 divisors (see below), whose sum is σ = 2124697120. Its totient is φ = 184218624.

The previous prime is 644781311. The next prime is 644781329. The reversal of 644781312 is 213187446.

644781312 is a `hidden beast` number, since 644 + 7 + 8 + 1 + 3 + 1 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644781311) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3862 + ... + 36117.

Almost surely, 2^644781312 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644781312, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1062348560).

644781312 is an abundant number, since it is smaller than the sum of its proper divisors (1479915808).

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

644781312 is a wasteful number, since it uses less digits than its factorization.

644781312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40008 (or 39991 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 644781312 is about 25392.5444176042. The cubic root of 644781312 is about 863.9146006127.

The spelling of 644781312 in words is "six hundred forty-four million, seven hundred eighty-one thousand, three hundred twelve".