644359398400 has 297 divisors, whose sum is σ = 1663824327841. Its totient is φ = 247417569280.

The previous prime is 644359398377. The next prime is 644359398433. The reversal of 644359398400 is 4893953446.

The square root of 644359398400 is 802720.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 13 ways, for example, as 108488549376 + 535870849024 = 329376^2 + 732032^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 3724620714 + ... + 3724620886.

Almost surely, 2^644359398400 is an apocalyptic number.

644359398400 is the 802720-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644359398400

644359398400 is an abundant number, since it is smaller than the sum of its proper divisors (1019464929441).

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

644359398400 is an equidigital number, since it uses as much as digits as its factorization.

644359398400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 434 (or 209 counting only the distinct ones).

The product of its (nonzero) digits is 11197440, while the sum is 55.

The spelling of 644359398400 in words is "six hundred forty-four billion, three hundred fifty-nine million, three hundred ninety-eight thousand, four hundred".