644372400 has 240 divisors, whose sum is σ = 2417845248. Its totient is φ = 143616000.

The previous prime is 644372321. The next prime is 644372401. The reversal of 644372400 is 4273446.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (644372401) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 343465 + ... + 345335.

Almost surely, 2^644372400 is an apocalyptic number.

644372400 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 644372400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1208922624).

644372400 is an abundant number, since it is smaller than the sum of its proper divisors (1773472848).

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

644372400 is a wasteful number, since it uses less digits than its factorization.

644372400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1940 (or 1929 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 30.

The square root of 644372400 is about 25384.4913283682. The cubic root of 644372400 is about 863.7319341564.

The spelling of 644372400 in words is "six hundred forty-four million, three hundred seventy-two thousand, four hundred".