644421671 has 2 divisors, whose sum is σ = 644421672. Its totient is φ = 644421670.

The previous prime is 644421593. The next prime is 644421683. The reversal of 644421671 is 176124446.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644421671 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644420671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322210835 + 322210836.

It is an arithmetic number, because the mean of its divisors is an integer number (322210836).

Almost surely, 2^644421671 is an apocalyptic number.

644421671 is a deficient number, since it is larger than the sum of its proper divisors (1).

644421671 is an equidigital number, since it uses as much as digits as its factorization.

644421671 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32256, while the sum is 35.

The square root of 644421671 is about 25385.4618039539. The cubic root of 644421671 is about 863.7539482647.

The spelling of 644421671 in words is "six hundred forty-four million, four hundred twenty-one thousand, six hundred seventy-one".