644221027 has 2 divisors, whose sum is σ = 644221028. Its totient is φ = 644221026.

The previous prime is 644221003. The next prime is 644221111. The reversal of 644221027 is 720122446.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644221027 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 644220986 and 644221004.

It is not a weakly prime, because it can be changed into another prime (644221327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322110513 + 322110514.

It is an arithmetic number, because the mean of its divisors is an integer number (322110514).

Almost surely, 2^644221027 is an apocalyptic number.

644221027 is a deficient number, since it is larger than the sum of its proper divisors (1).

644221027 is an equidigital number, since it uses as much as digits as its factorization.

644221027 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5376, while the sum is 28.

The square root of 644221027 is about 25381.5095492762. The cubic root of 644221027 is about 863.6642942153.

The spelling of 644221027 in words is "six hundred forty-four million, two hundred twenty-one thousand, twenty-seven".