644873441 has 4 divisors (see below), whose sum is σ = 652119300. Its totient is φ = 637627584.

The previous prime is 644873423. The next prime is 644873447. The reversal of 644873441 is 144378446.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 177449041 + 467424400 = 13321^2 + 21620^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644873441 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (644873447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3622796 + ... + 3622973.

It is an arithmetic number, because the mean of its divisors is an integer number (163029825).

Almost surely, 2^644873441 is an apocalyptic number.

It is an amenable number.

644873441 is a deficient number, since it is larger than the sum of its proper divisors (7245859).

644873441 is an equidigital number, since it uses as much as digits as its factorization.

644873441 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7245858.

The product of its digits is 258048, while the sum is 41.

The square root of 644873441 is about 25394.3584482853. The cubic root of 644873441 is about 863.9557452077.

The spelling of 644873441 in words is "six hundred forty-four million, eight hundred seventy-three thousand, four hundred forty-one".