644995800 has 72 divisors (see below), whose sum is σ = 2166116940. Its totient is φ = 171998400.

The previous prime is 644995783. The next prime is 644995811. The reversal of 644995800 is 8599446.

It is a happy number.

644995800 is a `hidden beast` number, since 64 + 4 + 9 + 9 + 580 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

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 polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 177366 + ... + 180965.

Almost surely, 2^644995800 is an apocalyptic number.

644995800 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644995800 is an abundant number, since it is smaller than the sum of its proper divisors (1521121140).

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

644995800 is a wasteful number, since it uses less digits than its factorization.

644995800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 358353 (or 358341 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The square root of 644995800 is about 25396.7675108467. The cubic root of 644995800 is about 864.0103843917.

The spelling of 644995800 in words is "six hundred forty-four million, nine hundred ninety-five thousand, eight hundred".