644587650 has 432 divisors, whose sum is σ = 2222857728. Its totient is φ = 133056000.

The previous prime is 644587649. The next prime is 644587679. The reversal of 644587650 is 56785446.

644587650 is a `hidden beast` number, since 6 + 4 + 4 + 587 + 65 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a junction number, because it is equal to n+sod(n) for n = 644587596 and 644587605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 215 ways as a sum of consecutive naturals, for example, 15721630 + ... + 15721670.

It is an arithmetic number, because the mean of its divisors is an integer number (5145504).

Almost surely, 2^644587650 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644587650, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1111428864).

644587650 is an abundant number, since it is smaller than the sum of its proper divisors (1578270078).

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

644587650 is a wasteful number, since it uses less digits than its factorization.

644587650 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127 (or 112 counting only the distinct ones).

The product of its (nonzero) digits is 806400, while the sum is 45.

The square root of 644587650 is about 25388.7307678033. The cubic root of 644587650 is about 863.8280988384.

The spelling of 644587650 in words is "six hundred forty-four million, five hundred eighty-seven thousand, six hundred fifty".