644221933 has 4 divisors (see below), whose sum is σ = 646987068. Its totient is φ = 641456800.

The previous prime is 644221909. The next prime is 644221969. The reversal of 644221933 is 339122446.

It is a happy number.

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 41126569 + 603095364 = 6413^2 + 24558^2 .

It is a cyclic number.

It is not a de Polignac number, because 644221933 - 2⁵ = 644221901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644221993) 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, 1382218 + ... + 1382683.

It is an arithmetic number, because the mean of its divisors is an integer number (161746767).

Almost surely, 2^644221933 is an apocalyptic number.

It is an amenable number.

644221933 is a deficient number, since it is larger than the sum of its proper divisors (2765135).

644221933 is a wasteful number, since it uses less digits than its factorization.

644221933 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2765134.

The product of its digits is 31104, while the sum is 34.

The square root of 644221933 is about 25381.5273969082. The cubic root of 644221933 is about 863.6646990864.

The spelling of 644221933 in words is "six hundred forty-four million, two hundred twenty-one thousand, nine hundred thirty-three".