644507136 has 480 divisors, whose sum is σ = 2412970560. Its totient is φ = 161021952.

The previous prime is 644507089. The next prime is 644507141. The reversal of 644507136 is 631705446.

It is a happy number.

644507136 is a `hidden beast` number, since 644 + 5 + 0 + 7 + 1 + 3 + 6 = 666.

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

It is a self number, because there is not a number n which added to its sum of digits gives 644507136.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 12160486 + ... + 12160538.

It is an arithmetic number, because the mean of its divisors is an integer number (5027022).

Almost surely, 2^644507136 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 644507136, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1206485280).

644507136 is an abundant number, since it is smaller than the sum of its proper divisors (1768463424).

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

644507136 is a wasteful number, since it uses less digits than its factorization.

644507136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 36.

The square root of 644507136 is about 25387.1450935311. The cubic root of 644507136 is about 863.7921310630.

The spelling of 644507136 in words is "six hundred forty-four million, five hundred seven thousand, one hundred thirty-six".