644600880 has 540 divisors, whose sum is σ = 2786290416. Its totient is φ = 133056000.

The previous prime is 644600863. The next prime is 644600899. The reversal of 644600880 is 88006446.

644600880 is a `hidden beast` number, since 6 + 44 + 600 + 8 + 8 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 107 ways as a sum of consecutive naturals, for example, 4268805 + ... + 4268955.

Almost surely, 2^644600880 is an apocalyptic number.

644600880 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 644600880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1393145208).

644600880 is an abundant number, since it is smaller than the sum of its proper divisors (2141689536).

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

644600880 is a wasteful number, since it uses less digits than its factorization.

644600880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 179 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 36.

The square root of 644600880 is about 25388.9913151350. The cubic root of 644600880 is about 863.8340087497.

The spelling of 644600880 in words is "six hundred forty-four million, six hundred thousand, eight hundred eighty".