644541100 has 108 divisors (see below), whose sum is σ = 1637655600. Its totient is φ = 219542400.

The previous prime is 644541097. The next prime is 644541103. The reversal of 644541100 is 1145446.

It is an interprime number because it is at equal distance from previous prime (644541097) and next prime (644541103).

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644541103) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 974770 + ... + 975430.

Almost surely, 2^644541100 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 644541100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (818827800).

644541100 is an abundant number, since it is smaller than the sum of its proper divisors (993114500).

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

644541100 is a wasteful number, since it uses less digits than its factorization.

644541100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 888 (or 874 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 644541100 is about 25387.8140059360. The cubic root of 644541100 is about 863.8073040631.

Adding to 644541100 its reverse (1145446), we get a palindrome (645686546).

The spelling of 644541100 in words is "six hundred forty-four million, five hundred forty-one thousand, one hundred".