644609271398400 has 7296 divisors, whose sum is σ = 3289315904593920. Its totient is φ = 120584562278400.

The previous prime is 644609271398329. The next prime is 644609271398501. The reversal of 644609271398400 is 4893172906446.

It is a happy number.

644609271398400 is a `hidden beast` number, since 6 + 4 + 4 + 6 + 0 + 92 + 7 + 139 + 8 + 400 = 666.

It is a super-2 number, since 2×644609271398400² (a number of 30 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

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 383 ways as a sum of consecutive naturals, for example, 28026490060789 + ... + 28026490060811.

Almost surely, 2^{644609271398400} is an apocalyptic number.

644609271398400 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 644609271398400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1644657952296960).

644609271398400 is an abundant number, since it is smaller than the sum of its proper divisors (2644706633195520).

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

644609271398400 is an equidigital number, since it uses as much as digits as its factorization.

644609271398400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 135 (or 68 counting only the distinct ones).

The product of its (nonzero) digits is 62705664, while the sum is 63.

The spelling of 644609271398400 in words is "six hundred forty-four trillion, six hundred nine billion, two hundred seventy-one million, three hundred ninety-eight thousand, four hundred".