644783632 has 40 divisors (see below), whose sum is σ = 1292417280. Its totient is φ = 311303040.

The previous prime is 644783627. The next prime is 644783707. The reversal of 644783632 is 236387446.

It is a happy number.

It is a super-2 number, since 2×644783632² = 831491864190222848, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 278094 + ... + 280402.

It is an arithmetic number, because the mean of its divisors is an integer number (32310432).

Almost surely, 2^644783632 is an apocalyptic number.

644783632 is a gapful number since it is divisible by the number (62) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644783632, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (646208640).

644783632 is an abundant number, since it is smaller than the sum of its proper divisors (647633648).

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

644783632 is a wasteful number, since it uses less digits than its factorization.

644783632 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2911 (or 2905 counting only the distinct ones).

The product of its digits is 580608, while the sum is 43.

The square root of 644783632 is about 25392.5901002635. The cubic root of 644783632 is about 863.9156367674.

The spelling of 644783632 in words is "six hundred forty-four million, seven hundred eighty-three thousand, six hundred thirty-two".