644575221 has 6 divisors (see below), whose sum is σ = 931053110. Its totient is φ = 429716808.

The previous prime is 644575201. The next prime is 644575259. The reversal of 644575221 is 122575446.

It is a happy number.

644575221 is a `hidden beast` number, since 64 + 4 + 575 + 2 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 436350321 + 208224900 = 20889^2 + 14430^2 .

It is not a de Polignac number, because 644575221 - 2⁷ = 644575093 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 (644575201) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35809726 + ... + 35809743.

Almost surely, 2^644575221 is an apocalyptic number.

It is an amenable number.

644575221 is a deficient number, since it is larger than the sum of its proper divisors (286477889).

644575221 is a wasteful number, since it uses less digits than its factorization.

644575221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71619475 (or 71619472 counting only the distinct ones).

The product of its digits is 67200, while the sum is 36.

The square root of 644575221 is about 25388.4859926700. The cubic root of 644575221 is about 863.8225466644.

The spelling of 644575221 in words is "six hundred forty-four million, five hundred seventy-five thousand, two hundred twenty-one".