161626991 has 2 divisors, whose sum is σ = 161626992. Its totient is φ = 161626990.

The previous prime is 161626943. The next prime is 161627009. The reversal of 161626991 is 199626161.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 161626991 - 2¹⁰ = 161625967 is a prime.

It is a super-2 number, since 2×161626991² = 52246568439428162, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161626921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80813495 + 80813496.

It is an arithmetic number, because the mean of its divisors is an integer number (80813496).

Almost surely, 2^161626991 is an apocalyptic number.

161626991 is a deficient number, since it is larger than the sum of its proper divisors (1).

161626991 is an equidigital number, since it uses as much as digits as its factorization.

161626991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34992, while the sum is 41.

The square root of 161626991 is about 12713.2604393995. The cubic root of 161626991 is about 544.7174598123.

The spelling of 161626991 in words is "one hundred sixty-one million, six hundred twenty-six thousand, nine hundred ninety-one".