644100 has 72 divisors (see below), whose sum is σ = 1979040. Its totient is φ = 161280.

The previous prime is 644089. The next prime is 644101. The reversal of 644100 is 1446.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 644100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644101) by changing a digit.

644100 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5644 + ... + 5756.

2⁶⁴⁴¹⁰⁰ is an apocalyptic number.

644100 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 644100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (989520).

644100 is an abundant number, since it is smaller than the sum of its proper divisors (1334940).

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

644100 is a wasteful number, since it uses less digits than its factorization.

644100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 149 (or 142 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 644100 is about 802.5584090893. The cubic root of 644100 is about 86.3610206544.

Adding to 644100 its reverse (1446), we get a palindrome (645546).

The spelling of 644100 in words is "six hundred forty-four thousand, one hundred".