644747445 has 20 divisors (see below), whose sum is σ = 1155770220. Its totient is φ = 343865088.

The previous prime is 644747443. The next prime is 644747471. The reversal of 644747445 is 544747446.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 308318481 + 336428964 = 17559^2 + 18342^2 .

It is not a de Polignac number, because 644747445 - 2¹ = 644747443 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 644747445.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644747443) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 795580 + ... + 796389.

It is an arithmetic number, because the mean of its divisors is an integer number (57788511).

Almost surely, 2^644747445 is an apocalyptic number.

It is an amenable number.

644747445 is a deficient number, since it is larger than the sum of its proper divisors (511022775).

644747445 is a wasteful number, since it uses less digits than its factorization.

644747445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1591986 (or 1591977 counting only the distinct ones).

The product of its digits is 1505280, while the sum is 45.

The square root of 644747445 is about 25391.8775398748. The cubic root of 644747445 is about 863.8994747049.

Subtracting from 644747445 its reverse (544747446), we obtain a palindrome (99999999).

The spelling of 644747445 in words is "six hundred forty-four million, seven hundred forty-seven thousand, four hundred forty-five".