644981832 has 128 divisors (see below), whose sum is σ = 1962576000. Its totient is φ = 194641920.

The previous prime is 644981807. The next prime is 644981851. The reversal of 644981832 is 238189446.

It is a happy number.

It is a super-2 number, since 2×644981832² = 832003127220152448, which contains 22 as substring.

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

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 838344 + ... + 839112.

It is an arithmetic number, because the mean of its divisors is an integer number (15332625).

Almost surely, 2^644981832 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 644981832, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (981288000).

644981832 is an abundant number, since it is smaller than the sum of its proper divisors (1317594168).

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

644981832 is a wasteful number, since it uses less digits than its factorization.

644981832 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148 (or 1138 counting only the distinct ones).

The product of its digits is 331776, while the sum is 45.

The square root of 644981832 is about 25396.4925137311. The cubic root of 644981832 is about 864.0041473566.

The spelling of 644981832 in words is "six hundred forty-four million, nine hundred eighty-one thousand, eight hundred thirty-two".