644794531920 has 1920 divisors, whose sum is σ = 2924812800000. Its totient is φ = 130828400640.

The previous prime is 644794531883. The next prime is 644794531951. The reversal of 644794531920 is 29135497446.

644794531920 is a `hidden beast` number, since 6 + 447 + 9 + 4 + 5 + 3 + 192 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 383 ways as a sum of consecutive naturals, for example, 4327480006 + ... + 4327480154.

It is an arithmetic number, because the mean of its divisors is an integer number (1523340000).

Almost surely, 2^644794531920 is an apocalyptic number.

644794531920 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 644794531920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1462406400000).

644794531920 is an abundant number, since it is smaller than the sum of its proper divisors (2280018268080).

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

644794531920 is a wasteful number, since it uses less digits than its factorization.

644794531920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268 (or 236 counting only the distinct ones).

The product of its (nonzero) digits is 6531840, while the sum is 54.

The spelling of 644794531920 in words is "six hundred forty-four billion, seven hundred ninety-four million, five hundred thirty-one thousand, nine hundred twenty".