644582221 has 4 divisors (see below), whose sum is σ = 644983452. Its totient is φ = 644180992.

The previous prime is 644582219. The next prime is 644582243. The reversal of 644582221 is 122285446.

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 411684100 + 232898121 = 20290^2 + 15261^2 .

It is a cyclic number.

It is not a de Polignac number, because 644582221 - 2¹ = 644582219 is a prime.

It is a super-3 number, since 3×644582221³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644582261) 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, 198196 + ... + 201421.

It is an arithmetic number, because the mean of its divisors is an integer number (161245863).

Almost surely, 2^644582221 is an apocalyptic number.

It is an amenable number.

644582221 is a deficient number, since it is larger than the sum of its proper divisors (401231).

644582221 is a wasteful number, since it uses less digits than its factorization.

644582221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 401230.

The product of its digits is 30720, while the sum is 34.

The square root of 644582221 is about 25388.6238500632. The cubic root of 644582221 is about 863.8256736519.

The spelling of 644582221 in words is "six hundred forty-four million, five hundred eighty-two thousand, two hundred twenty-one".