644722019 has 2 divisors, whose sum is σ = 644722020. Its totient is φ = 644722018.

The previous prime is 644721943. The next prime is 644722027. The reversal of 644722019 is 910227446.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644722019 - 2¹² = 644717923 is a prime.

It is a super-2 number, since 2×644722019² = 831332963566872722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 644722019.

It is not a weakly prime, because it can be changed into another prime (644722049) 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, 322361009 + 322361010.

It is an arithmetic number, because the mean of its divisors is an integer number (322361010).

Almost surely, 2^644722019 is an apocalyptic number.

644722019 is a deficient number, since it is larger than the sum of its proper divisors (1).

644722019 is an equidigital number, since it uses as much as digits as its factorization.

644722019 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 35.

The square root of 644722019 is about 25391.3768630218. The cubic root of 644722019 is about 863.8881184253. Note that the first 3 decimals are identical.

The spelling of 644722019 in words is "six hundred forty-four million, seven hundred twenty-two thousand, nineteen".