644221439 has 2 divisors, whose sum is σ = 644221440. Its totient is φ = 644221438.

The previous prime is 644221327. The next prime is 644221453. The reversal of 644221439 is 934122446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644221439 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 644221399 and 644221408.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644221499) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322110719 + 322110720.

It is an arithmetic number, because the mean of its divisors is an integer number (322110720).

Almost surely, 2^644221439 is an apocalyptic number.

644221439 is a deficient number, since it is larger than the sum of its proper divisors (1).

644221439 is an equidigital number, since it uses as much as digits as its factorization.

644221439 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 41472, while the sum is 35.

The square root of 644221439 is about 25381.5176654195. The cubic root of 644221439 is about 863.6644783289.

The spelling of 644221439 in words is "six hundred forty-four million, two hundred twenty-one thousand, four hundred thirty-nine".