8643991 has 2 divisors, whose sum is σ = 8643992. Its totient is φ = 8643990.

The previous prime is 8643959. The next prime is 8643997. The reversal of 8643991 is 1993468.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 8643991 - 2⁵ = 8643959 is a prime.

8643991 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8643997) 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, 4321995 + 4321996.

It is an arithmetic number, because the mean of its divisors is an integer number (4321996).

Almost surely, 2^8643991 is an apocalyptic number.

8643991 is a deficient number, since it is larger than the sum of its proper divisors (1).

8643991 is an equidigital number, since it uses as much as digits as its factorization.

8643991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 46656, while the sum is 40.

The square root of 8643991 is about 2940.0664958467. The cubic root of 8643991 is about 205.2287037099.

The spelling of 8643991 in words is "eight million, six hundred forty-three thousand, nine hundred ninety-one".