644829720 has 128 divisors (see below), whose sum is σ = 2096202240. Its totient is φ = 158054400.

The previous prime is 644829709. The next prime is 644829727. The reversal of 644829720 is 27928446.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644829727) 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, 84045 + ... + 91395.

It is an arithmetic number, because the mean of its divisors is an integer number (16376580).

Almost surely, 2^644829720 is an apocalyptic number.

644829720 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 644829720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1048101120).

644829720 is an abundant number, since it is smaller than the sum of its proper divisors (1451372520).

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

644829720 is a wasteful number, since it uses less digits than its factorization.

644829720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7425 (or 7421 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 42.

The square root of 644829720 is about 25393.4975928878. The cubic root of 644829720 is about 863.9362200004.

The spelling of 644829720 in words is "six hundred forty-four million, eight hundred twenty-nine thousand, seven hundred twenty".