644041720 has 32 divisors (see below), whose sum is σ = 1656108000. Its totient is φ = 220814208.

The previous prime is 644041687. The next prime is 644041747. The reversal of 644041720 is 27140446.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

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, 1149795 + ... + 1150354.

It is an arithmetic number, because the mean of its divisors is an integer number (51753375).

Almost surely, 2^644041720 is an apocalyptic number.

It is an amenable number.

644041720 is an abundant number, since it is smaller than the sum of its proper divisors (1012066280).

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

644041720 is a wasteful number, since it uses less digits than its factorization.

644041720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2300167 (or 2300163 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 28.

The square root of 644041720 is about 25377.9770667404. The cubic root of 644041720 is about 863.5841584560.

The spelling of 644041720 in words is "six hundred forty-four million, forty-one thousand, seven hundred twenty".