644005221 has 8 divisors (see below), whose sum is σ = 896007360. Its totient is φ = 410669952.

The previous prime is 644005199. The next prime is 644005277. The reversal of 644005221 is 122500446.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 644005221 - 2⁷ = 644005093 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 644005191 and 644005200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644005321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4666636 + ... + 4666773.

It is an arithmetic number, because the mean of its divisors is an integer number (112000920).

Almost surely, 2^644005221 is an apocalyptic number.

It is an amenable number.

644005221 is a deficient number, since it is larger than the sum of its proper divisors (252002139).

644005221 is a wasteful number, since it uses less digits than its factorization.

644005221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9333435.

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 644005221 is about 25377.2579488013. The cubic root of 644005221 is about 863.5678445265.

Adding to 644005221 its reverse (122500446), we get a palindrome (766505667).

The spelling of 644005221 in words is "six hundred forty-four million, five thousand, two hundred twenty-one".