644700 has 72 divisors (see below), whose sum is σ = 2138752. Its totient is φ = 146880.

The previous prime is 644687. The next prime is 644701. The reversal of 644700 is 7446.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644701) by changing a digit.

644700 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 23 ways as a sum of consecutive naturals, for example, 1947 + ... + 2253.

2⁶⁴⁴⁷⁰⁰ is an apocalyptic number.

644700 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 644700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1069376).

644700 is an abundant number, since it is smaller than the sum of its proper divisors (1494052).

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

644700 is a wasteful number, since it uses less digits than its factorization.

644700 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 331 (or 324 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 644700 is about 802.9321266458. The cubic root of 644700 is about 86.3878283608.

The spelling of 644700 in words is "six hundred forty-four thousand, seven hundred".