644750400 has 336 divisors, whose sum is σ = 2499522560. Its totient is φ = 142387200.

The previous prime is 644750387. The next prime is 644750437. The reversal of 644750400 is 4057446.

It is a tau number, because it is divible by the number of its divisors (336).

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

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1041291 + ... + 1041909.

Almost surely, 2^644750400 is an apocalyptic number.

644750400 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 644750400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1249761280).

644750400 is an abundant number, since it is smaller than the sum of its proper divisors (1854772160).

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

644750400 is a wasteful number, since it uses less digits than its factorization.

644750400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 682 (or 667 counting only the distinct ones).

The product of its (nonzero) digits is 13440, while the sum is 30.

The square root of 644750400 is about 25391.9357277069. The cubic root of 644750400 is about 863.9007945080.

The spelling of 644750400 in words is "six hundred forty-four million, seven hundred fifty thousand, four hundred".