644420740 has 24 divisors (see below), whose sum is σ = 1373484672. Its totient is φ = 253920480.

The previous prime is 644420731. The next prime is 644420759. The reversal of 644420740 is 47024446.

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 7 ways as a sum of consecutive naturals, for example, 239116 + ... + 241795.

It is an arithmetic number, because the mean of its divisors is an integer number (57228528).

Almost surely, 2^644420740 is an apocalyptic number.

It is an amenable number.

644420740 is an abundant number, since it is smaller than the sum of its proper divisors (729063932).

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

644420740 is a wasteful number, since it uses less digits than its factorization.

644420740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 480987 (or 480985 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 31.

The square root of 644420740 is about 25385.4434666799. The cubic root of 644420740 is about 863.7535323076.

The spelling of 644420740 in words is "six hundred forty-four million, four hundred twenty thousand, seven hundred forty".