644392980 has 288 divisors, whose sum is σ = 2566287360. Its totient is φ = 126800640.

The previous prime is 644392979. The next prime is 644393003. The reversal of 644392980 is 89293446.

It is a super-5 number, since 5×644392980⁵ (a number of 45 digits) contains 55555 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

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 95 ways as a sum of consecutive naturals, for example, 262117 + ... + 264563.

It is an arithmetic number, because the mean of its divisors is an integer number (8910720).

Almost surely, 2^644392980 is an apocalyptic number.

644392980 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 644392980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1283143680).

644392980 is an abundant number, since it is smaller than the sum of its proper divisors (1921894380).

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

644392980 is a wasteful number, since it uses less digits than its factorization.

644392980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2499 (or 2494 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 644392980 is about 25384.8966907490. The cubic root of 644392980 is about 863.7411293640.

The spelling of 644392980 in words is "six hundred forty-four million, three hundred ninety-two thousand, nine hundred eighty".