640544 has 24 divisors (see below), whose sum is σ = 1297548. Its totient is φ = 311040.

The previous prime is 640531. The next prime is 640579. The reversal of 640544 is 445046.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 620944 + 19600 = 788^2 + 140^2 .

It is an unprimeable 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 3 ways as a sum of consecutive naturals, for example, 914 + ... + 1454.

2⁶⁴⁰⁵⁴⁴ 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 640544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (648774).

640544 is an abundant number, since it is smaller than the sum of its proper divisors (657004).

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

640544 is a wasteful number, since it uses less digits than its factorization.

640544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 588 (or 580 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 23.

The square root of 640544 is about 800.3399277807. The cubic root of 640544 is about 86.2017976129.

The spelling of 640544 in words is "six hundred forty thousand, five hundred forty-four".