644606240 has 96 divisors (see below), whose sum is σ = 1555965936. Its totient is φ = 252313600.

The previous prime is 644606233. The next prime is 644606243. The reversal of 644606240 is 42606446.

It can be written as a sum of positive squares in 8 ways, for example, as 226321936 + 418284304 = 15044^2 + 20452^2 .

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a junction number, because it is equal to n+sod(n) for n = 644606197 and 644606206.

It is not an unprimeable number, because it can be changed into a prime (644606243) 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, 1825904 + ... + 1826256.

Almost surely, 2^644606240 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 644606240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (777982968).

644606240 is an abundant number, since it is smaller than the sum of its proper divisors (911359696).

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

644606240 is a wasteful number, since it uses less digits than its factorization.

644606240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 582 (or 574 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 32.

The square root of 644606240 is about 25389.0968724766. The cubic root of 644606240 is about 863.8364030672.

The spelling of 644606240 in words is "six hundred forty-four million, six hundred six thousand, two hundred forty".