644008400 has 60 divisors (see below), whose sum is σ = 1768270752. Its totient is φ = 220801920.

The previous prime is 644008397. The next prime is 644008403. The reversal of 644008400 is 4800446.

It is an interprime number because it is at equal distance from previous prime (644008397) and next prime (644008403).

It is a self number, because there is not a number n which added to its sum of digits gives 644008400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644008403) by changing a digit.

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, 112202 + ... + 117801.

Almost surely, 2^644008400 is an apocalyptic number.

It is an amenable number.

644008400 is an abundant number, since it is smaller than the sum of its proper divisors (1124262352).

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

644008400 is a wasteful number, since it uses less digits than its factorization.

644008400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230028 (or 230017 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 26.

The square root of 644008400 is about 25377.3205835447. The cubic root of 644008400 is about 863.5692654662.

Adding to 644008400 its reverse (4800446), we get a palindrome (648808846).

The spelling of 644008400 in words is "six hundred forty-four million, eight thousand, four hundred".