644221111 has 2 divisors, whose sum is σ = 644221112. Its totient is φ = 644221110.

The previous prime is 644221027. The next prime is 644221133. The reversal of 644221111 is 111122446.

It is an a-pointer prime, because the next prime (644221133) can be obtained adding 644221111 to its sum of digits (22).

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644221111 - 2¹⁵ = 644188343 is a prime.

It is a Chen prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644221181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322110555 + 322110556.

It is an arithmetic number, because the mean of its divisors is an integer number (322110556).

Almost surely, 2^644221111 is an apocalyptic number.

644221111 is a deficient number, since it is larger than the sum of its proper divisors (1).

644221111 is an equidigital number, since it uses as much as digits as its factorization.

644221111 is an evil number, because the sum of its binary digits is even.

The product of its digits is 384, while the sum is 22.

The square root of 644221111 is about 25381.5112040241. The cubic root of 644221111 is about 863.6643317530.

Adding to 644221111 its reverse (111122446), we get a palindrome (755343557).

The spelling of 644221111 in words is "six hundred forty-four million, two hundred twenty-one thousand, one hundred eleven".