644022625 has 8 divisors (see below), whose sum is σ = 803740392. Its totient is φ = 515218000.

The previous prime is 644022581. The next prime is 644022649. The reversal of 644022625 is 526220446.

It can be written as a sum of positive squares in 4 ways, for example, as 64128064 + 579894561 = 8008^2 + 24081^2 .

It is not a de Polignac number, because 644022625 - 2¹⁹ = 643498337 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2575966 + ... + 2576215.

It is an arithmetic number, because the mean of its divisors is an integer number (100467549).

Almost surely, 2^644022625 is an apocalyptic number.

It is an amenable number.

644022625 is a deficient number, since it is larger than the sum of its proper divisors (159717767).

644022625 is an equidigital number, since it uses as much as digits as its factorization.

644022625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5152196 (or 5152186 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 31.

The square root of 644022625 is about 25377.6008519324. The cubic root of 644022625 is about 863.5756236557.

The spelling of 644022625 in words is "six hundred forty-four million, twenty-two thousand, six hundred twenty-five".