168406991 has 2 divisors, whose sum is σ = 168406992. Its totient is φ = 168406990.

The previous prime is 168406949. The next prime is 168407009. The reversal of 168406991 is 199604861.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 168406991 - 2¹⁰ = 168405967 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (168406921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 84203495 + 84203496.

It is an arithmetic number, because the mean of its divisors is an integer number (84203496).

Almost surely, 2^168406991 is an apocalyptic number.

168406991 is a deficient number, since it is larger than the sum of its proper divisors (1).

168406991 is an equidigital number, since it uses as much as digits as its factorization.

168406991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 93312, while the sum is 44.

The square root of 168406991 is about 12977.1719184112. The cubic root of 168406991 is about 552.2300542429.

The spelling of 168406991 in words is "one hundred sixty-eight million, four hundred six thousand, nine hundred ninety-one".