644377735961280 has 560 divisors, whose sum is σ = 2372652164146176. Its totient is φ = 165873411809280.

The previous prime is 644377735961279. The next prime is 644377735961293. The reversal of 644377735961280 is 82169537773446.

644377735961280 is a `hidden beast` number, since 6 + 4 + 4 + 3 + 7 + 7 + 7 + 3 + 596 + 1 + 28 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 644377735961199 and 644377735961208.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 119152810 + ... + 124443350.

It is a 1-persistent number, because it is pandigital, but 2⋅644377735961280 = 1288755471922560 is not.

Almost surely, 2^{644377735961280} is an apocalyptic number.

644377735961280 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 644377735961280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1186326082073088).

644377735961280 is an abundant number, since it is smaller than the sum of its proper divisors (1728274428184896).

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

644377735961280 is a wasteful number, since it uses less digits than its factorization.

644377735961280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5290734 (or 5290715 counting only the distinct ones).

The product of its (nonzero) digits is 1280240640, while the sum is 72.

The spelling of 644377735961280 in words is "six hundred forty-four trillion, three hundred seventy-seven billion, seven hundred thirty-five million, nine hundred sixty-one thousand, two hundred eighty".