644499040 has 96 divisors (see below), whose sum is σ = 1554958944. Its totient is φ = 252395520.

The previous prime is 644499029. The next prime is 644499043. The reversal of 644499040 is 40994446.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 644498984 and 644499002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644499043) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2032962 + ... + 2033278.

It is an arithmetic number, because the mean of its divisors is an integer number (16197489).

Almost surely, 2^644499040 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 644499040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (777479472).

644499040 is an abundant number, since it is smaller than the sum of its proper divisors (910459904).

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

644499040 is a wasteful number, since it uses less digits than its factorization.

644499040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 560 (or 552 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 40.

The square root of 644499040 is about 25386.9856422538. The cubic root of 644499040 is about 863.7885141957.

The spelling of 644499040 in words is "six hundred forty-four million, four hundred ninety-nine thousand, forty".