644280720 has 80 divisors (see below), whose sum is σ = 2034994752. Its totient is φ = 168563200.

The previous prime is 644280697. The next prime is 644280727. The reversal of 644280720 is 27082446.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (644280727) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12606 + ... + 38045.

Almost surely, 2^644280720 is an apocalyptic number.

644280720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644280720 is an abundant number, since it is smaller than the sum of its proper divisors (1390714032).

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

644280720 is a wasteful number, since it uses less digits than its factorization.

644280720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50720 (or 50714 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 33.

The square root of 644280720 is about 25382.6854371243. The cubic root of 644280720 is about 863.6909688701.

The spelling of 644280720 in words is "six hundred forty-four million, two hundred eighty thousand, seven hundred twenty".