644506547 has 4 divisors (see below), whose sum is σ = 653584176. Its totient is φ = 635428920.

The previous prime is 644506519. The next prime is 644506571. The reversal of 644506547 is 745605446.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 745605446 = 2 ⋅372802723.

It is a cyclic number.

It is not a de Polignac number, because 644506547 - 2¹⁰ = 644505523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644506517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4538708 + ... + 4538849.

It is an arithmetic number, because the mean of its divisors is an integer number (163396044).

Almost surely, 2^644506547 is an apocalyptic number.

644506547 is a deficient number, since it is larger than the sum of its proper divisors (9077629).

644506547 is an equidigital number, since it uses as much as digits as its factorization.

644506547 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9077628.

The product of its (nonzero) digits is 403200, while the sum is 41.

The square root of 644506547 is about 25387.1334931693. The cubic root of 644506547 is about 863.7918679298.

The spelling of 644506547 in words is "six hundred forty-four million, five hundred six thousand, five hundred forty-seven".