643161791 has 2 divisors, whose sum is σ = 643161792. Its totient is φ = 643161790.

The previous prime is 643161769. The next prime is 643161821. The reversal of 643161791 is 197161346.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643161791 - 2²⁶ = 576052927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643161721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321580895 + 321580896.

It is an arithmetic number, because the mean of its divisors is an integer number (321580896).

Almost surely, 2^643161791 is an apocalyptic number.

643161791 is a deficient number, since it is larger than the sum of its proper divisors (1).

643161791 is an equidigital number, since it uses as much as digits as its factorization.

643161791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 38.

The square root of 643161791 is about 25360.6346726575. The cubic root of 643161791 is about 863.1906854584.

The spelling of 643161791 in words is "six hundred forty-three million, one hundred sixty-one thousand, seven hundred ninety-one".