644280 has 128 divisors (see below), whose sum is σ = 2419200. Its totient is φ = 133632.

The previous prime is 644261. The next prime is 644291. The reversal of 644280 is 82446.

644280 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 644280.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 644280.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10891 + ... + 10949.

It is an arithmetic number, because the mean of its divisors is an integer number (18900).

2⁶⁴⁴²⁸⁰ is an apocalyptic number.

644280 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 644280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1209600).

644280 is an abundant number, since it is smaller than the sum of its proper divisors (1774920).

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

644280 is a wasteful number, since it uses less digits than its factorization.

644280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 89 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 644280 is about 802.6705426263. The cubic root of 644280 is about 86.3690647138.

Adding to 644280 its product of nonzero digits (1536), we get a triangular number (645816 = T₁₁₃₆).

The spelling of 644280 in words is "six hundred forty-four thousand, two hundred eighty".