644440219 has 2 divisors, whose sum is σ = 644440220. Its totient is φ = 644440218.

The previous prime is 644440217. The next prime is 644440229. The reversal of 644440219 is 912044446.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644440219 - 2¹ = 644440217 is a prime.

It is a super-2 number, since 2×644440219² = 830606391729535922, which contains 22 as substring.

Together with 644440217, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (644440217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322220109 + 322220110.

It is an arithmetic number, because the mean of its divisors is an integer number (322220110).

Almost surely, 2^644440219 is an apocalyptic number.

644440219 is a deficient number, since it is larger than the sum of its proper divisors (1).

644440219 is an equidigital number, since it uses as much as digits as its factorization.

644440219 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27648, while the sum is 34.

The square root of 644440219 is about 25385.8271285377. The cubic root of 644440219 is about 863.7622351547.

The spelling of 644440219 in words is "six hundred forty-four million, four hundred forty thousand, two hundred nineteen".