644600 has 48 divisors (see below), whose sum is σ = 1640520. Its totient is φ = 233600.

The previous prime is 644599. The next prime is 644617. The reversal of 644600 is 6446.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2054 + ... + 2346.

2⁶⁴⁴⁶⁰⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (820260).

644600 is an abundant number, since it is smaller than the sum of its proper divisors (995920).

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

644600 is a wasteful number, since it uses less digits than its factorization.

644600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320 (or 311 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 644600 is about 802.8698524668. The cubic root of 644600 is about 86.3833615652.

Multiplying 644600 by its reverse (6446), we get a square (4155091600 = 64460²).

644600 divided by its reverse (6446) gives a square (100 = 10²).

It can be divided in two parts, 64 and 4600, that added together give a palindrome (4664).

The spelling of 644600 in words is "six hundred forty-four thousand, six hundred".