644900 has 18 divisors (see below), whose sum is σ = 1399650. Its totient is φ = 257920.

The previous prime is 644899. The next prime is 644909. The reversal of 644900 is 9446.

644900 = T₇ + T₈ + ... + T₁₅₆.

644900 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 3 ways, for example, as 179776 + 465124 = 424^2 + 682^2 .

It is not an unprimeable number, because it can be changed into a prime (644909) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3125 + ... + 3324.

2⁶⁴⁴⁹⁰⁰ is an apocalyptic number.

It is an amenable number.

644900 is an abundant number, since it is smaller than the sum of its proper divisors (754750).

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

644900 is a wasteful number, since it uses less digits than its factorization.

644900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6463 (or 6456 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 644900 is about 803.0566605166. The cubic root of 644900 is about 86.3967605667.

It can be divided in two parts, 64 and 4900, that multiplied together give a square (313600 = 560²).

The spelling of 644900 in words is "six hundred forty-four thousand, nine hundred".