644040606 has 48 divisors (see below), whose sum is σ = 1483083648. Its totient is φ = 184885200.

The previous prime is 644040601. The next prime is 644040619. The reversal of 644040606 is 606040446.

It is a hoax number, since the sum of its digits (30) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644040601) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10311 + ... + 37341.

It is an arithmetic number, because the mean of its divisors is an integer number (30897576).

Almost surely, 2^644040606 is an apocalyptic number.

644040606 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 644040606, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (741541824).

644040606 is an abundant number, since it is smaller than the sum of its proper divisors (839043042).

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

644040606 is a wasteful number, since it uses less digits than its factorization.

644040606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27085 (or 27066 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 30.

The square root of 644040606 is about 25377.9551185670. The cubic root of 644040606 is about 863.5836605415.

The spelling of 644040606 in words is "six hundred forty-four million, forty thousand, six hundred six".