128166991 has 2 divisors, whose sum is σ = 128166992. Its totient is φ = 128166990.

The previous prime is 128166977. The next prime is 128167007. The reversal of 128166991 is 199661821.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 128166991 - 2⁵ = 128166959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128166911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64083495 + 64083496.

It is an arithmetic number, because the mean of its divisors is an integer number (64083496).

Almost surely, 2^128166991 is an apocalyptic number.

128166991 is a deficient number, since it is larger than the sum of its proper divisors (1).

128166991 is an equidigital number, since it uses as much as digits as its factorization.

128166991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46656, while the sum is 43.

The square root of 128166991 is about 11321.0861228064. The cubic root of 128166991 is about 504.1874866737.

The spelling of 128166991 in words is "one hundred twenty-eight million, one hundred sixty-six thousand, nine hundred ninety-one".