644255136000 has 1296 divisors, whose sum is σ = 2738937172608. Its totient is φ = 144958464000.

The previous prime is 644255135957. The next prime is 644255136013. The reversal of 644255136000 is 631552446.

644255136000 is a `hidden beast` number, since 6 + 4 + 42 + 5 + 5 + 1 + 3 + 600 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 1001951679 + ... + 1001952321.

It is an arithmetic number, because the mean of its divisors is an integer number (2113377448).

Almost surely, 2^644255136000 is an apocalyptic number.

644255136000 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 644255136000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1369468586304).

644255136000 is an abundant number, since it is smaller than the sum of its proper divisors (2094682036608).

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

644255136000 is a wasteful number, since it uses less digits than its factorization.

644255136000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 765 (or 731 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 36.

Adding to 644255136000 its reverse (631552446), we get a palindrome (644886688446).

The spelling of 644255136000 in words is "six hundred forty-four billion, two hundred fifty-five million, one hundred thirty-six thousand".