644513234441520 has 80 divisors (see below), whose sum is σ = 1998111990147840. Its totient is φ = 171859790399232.

The previous prime is 644513234441491. The next prime is 644513234441579. The reversal of 644513234441520 is 25144432315446.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is a self number, because there is not a number n which added to its sum of digits gives 644513234441520.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77319774 + ... + 85248893.

It is an arithmetic number, because the mean of its divisors is an integer number (24976399876848).

Almost surely, 2^{644513234441520} is an apocalyptic number.

644513234441520 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

644513234441520 is an abundant number, since it is smaller than the sum of its proper divisors (1353598755706320).

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

644513234441520 is a wasteful number, since it uses less digits than its factorization.

644513234441520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162585202 (or 162585196 counting only the distinct ones).

The product of its (nonzero) digits is 5529600, while the sum is 48.

Adding to 644513234441520 its reverse (25144432315446), we get a palindrome (669657666756966).

The spelling of 644513234441520 in words is "six hundred forty-four trillion, five hundred thirteen billion, two hundred thirty-four million, four hundred forty-one thousand, five hundred twenty".