644646445 has 8 divisors (see below), whose sum is σ = 776017944. Its totient is φ = 514089024.

The previous prime is 644646439. The next prime is 644646451. The reversal of 644646445 is 544646446.

It is an interprime number because it is at equal distance from previous prime (644646439) and next prime (644646451).

It can be written as a sum of positive squares in 4 ways, for example, as 68790436 + 575856009 = 8294^2 + 23997^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 644646445 - 2⁵ = 644646413 is a prime.

It is a super-2 number, since 2×644646445² = 831138078102276050, which contains 22 as substring.

It is a Duffinian number.

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, 201774 + ... + 204943.

It is an arithmetic number, because the mean of its divisors is an integer number (97002243).

Almost surely, 2^644646445 is an apocalyptic number.

It is an amenable number.

644646445 is a deficient number, since it is larger than the sum of its proper divisors (131371499).

644646445 is a wasteful number, since it uses less digits than its factorization.

644646445 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 407039.

The product of its digits is 1105920, while the sum is 43.

The square root of 644646445 is about 25389.8886370145. Note that the first 3 decimals coincide. The cubic root of 644646445 is about 863.8543622586.

Subtracting from 644646445 its reverse (544646446), we obtain a palindrome (99999999).

The spelling of 644646445 in words is "six hundred forty-four million, six hundred forty-six thousand, four hundred forty-five".