644025720 has 128 divisors (see below), whose sum is σ = 2089281600. Its totient is φ = 157876224.

The previous prime is 644025719. The next prime is 644025727. The reversal of 644025720 is 27520446.

It is a super-5 number, since 5×644025720⁵ (a number of 45 digits) contains 55555 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644025727) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 456376 + ... + 457784.

Almost surely, 2^644025720 is an apocalyptic number.

644025720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644025720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1044640800).

644025720 is an abundant number, since it is smaller than the sum of its proper divisors (1445255880).

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

644025720 is a wasteful number, since it uses less digits than its factorization.

644025720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1729 (or 1725 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 30.

The square root of 644025720 is about 25377.6618308307. The cubic root of 644025720 is about 863.5770070244.

The spelling of 644025720 in words is "six hundred forty-four million, twenty-five thousand, seven hundred twenty".