644161900 has 36 divisors (see below), whose sum is σ = 1404502120. Its totient is φ = 256435200.

The previous prime is 644161879. The next prime is 644161933. The reversal of 644161900 is 9161446.

It is a super-2 number, since 2×644161900² = 829889106823220000, which contains 22 as substring.

It is a zygodrome in base 3.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5836 + ... + 36364.

Almost surely, 2^644161900 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 644161900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (702251060).

644161900 is an abundant number, since it is smaller than the sum of its proper divisors (760340220).

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

644161900 is a wasteful number, since it uses less digits than its factorization.

644161900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30754 (or 30747 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 644161900 is about 25380.3447573117. The cubic root of 644161900 is about 863.6378708611.

The spelling of 644161900 in words is "six hundred forty-four million, one hundred sixty-one thousand, nine hundred".