644146566 has 64 divisors (see below), whose sum is σ = 1509580800. Its totient is φ = 179446176.

The previous prime is 644146561. The next prime is 644146583. The reversal of 644146566 is 665641446.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644146561) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 274225 + ... + 276563.

It is an arithmetic number, because the mean of its divisors is an integer number (23587200).

Almost surely, 2^644146566 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 644146566, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (754790400).

644146566 is an abundant number, since it is smaller than the sum of its proper divisors (865434234).

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

644146566 is a wasteful number, since it uses less digits than its factorization.

644146566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2513.

The product of its digits is 414720, while the sum is 42.

The square root of 644146566 is about 25380.0426713589. The cubic root of 644146566 is about 863.6310179627.

The spelling of 644146566 in words is "six hundred forty-four million, one hundred forty-six thousand, five hundred sixty-six".