644960436 has 12 divisors (see below), whose sum is σ = 1504907712. Its totient is φ = 214986808.

The previous prime is 644960413. The next prime is 644960471. The reversal of 644960436 is 634069446.

It is a tau number, because it is divible by the number of its divisors (12).

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26873340 + ... + 26873363.

It is an arithmetic number, because the mean of its divisors is an integer number (125408976).

Almost surely, 2^644960436 is an apocalyptic number.

It is an amenable number.

644960436 is an abundant number, since it is smaller than the sum of its proper divisors (859947276).

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

644960436 is a wasteful number, since it uses less digits than its factorization.

644960436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53746710 (or 53746708 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 42.

The square root of 644960436 is about 25396.0712709663. The cubic root of 644960436 is about 863.9945933732.

The spelling of 644960436 in words is "six hundred forty-four million, nine hundred sixty thousand, four hundred thirty-six".