644134860 has 144 divisors (see below), whose sum is σ = 2006484480. Its totient is φ = 167207040.

The previous prime is 644134787. The next prime is 644134889. The reversal of 644134860 is 68431446.

644134860 is a `hidden beast` number, since 644 + 1 + 3 + 4 + 8 + 6 + 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 47 ways as a sum of consecutive naturals, for example, 1390989 + ... + 1391451.

It is an arithmetic number, because the mean of its divisors is an integer number (13933920).

Almost surely, 2^644134860 is an apocalyptic number.

644134860 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 644134860, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1003242240).

644134860 is an abundant number, since it is smaller than the sum of its proper divisors (1362349620).

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

644134860 is a wasteful number, since it uses less digits than its factorization.

644134860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 668 (or 663 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 36.

The square root of 644134860 is about 25379.8120560417. The cubic root of 644134860 is about 863.6257863760.

The spelling of 644134860 in words is "six hundred forty-four million, one hundred thirty-four thousand, eight hundred sixty".