644643040 has 48 divisors (see below), whose sum is σ = 1524755232. Its totient is φ = 257554944.

The previous prime is 644643031. The next prime is 644643053. The reversal of 644643040 is 40346446.

It is a junction number, because it is equal to n+sod(n) for n = 644642993 and 644643011.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 176917 + ... + 180523.

It is an arithmetic number, because the mean of its divisors is an integer number (31765734).

Almost surely, 2^644643040 is an apocalyptic number.

It is an amenable number.

644643040 is an abundant number, since it is smaller than the sum of its proper divisors (880112192).

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

644643040 is a wasteful number, since it uses less digits than its factorization.

644643040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4739 (or 4731 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 31.

The square root of 644643040 is about 25389.8215826736. The cubic root of 644643040 is about 863.8528413064.

Adding to 644643040 its reverse (40346446), we get a palindrome (684989486).

The spelling of 644643040 in words is "six hundred forty-four million, six hundred forty-three thousand, forty".