644641100 has 72 divisors (see below), whose sum is σ = 1427877360. Its totient is φ = 252564480.

The previous prime is 644641099. The next prime is 644641159. The reversal of 644641100 is 1146446.

It is a self number, because there is not a number n which added to its sum of digits gives 644641100.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1700711 + ... + 1701089.

It is an arithmetic number, because the mean of its divisors is an integer number (19831630).

Almost surely, 2^644641100 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644641100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (713938680).

644641100 is an abundant number, since it is smaller than the sum of its proper divisors (783236260).

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

644641100 is a wasteful number, since it uses less digits than its factorization.

644641100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 699 (or 692 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 644641100 is about 25389.7833783591. The cubic root of 644641100 is about 863.8519747410.

Adding to 644641100 its reverse (1146446), we get a palindrome (645787546).

The spelling of 644641100 in words is "six hundred forty-four million, six hundred forty-one thousand, one hundred".