161161991 has 8 divisors (see below), whose sum is σ = 162169680. Its totient is φ = 160157952.

The previous prime is 161161969. The next prime is 161161993. The reversal of 161161991 is 199161161.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161161991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161161993) 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 in 7 ways as a sum of consecutive naturals, for example, 173015 + ... + 173943.

It is an arithmetic number, because the mean of its divisors is an integer number (20271210).

Almost surely, 2^161161991 is an apocalyptic number.

161161991 is a deficient number, since it is larger than the sum of its proper divisors (1007689).

161161991 is an equidigital number, since it uses as much as digits as its factorization.

161161991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1825.

The product of its digits is 2916, while the sum is 35.

The square root of 161161991 is about 12694.9592752399. The cubic root of 161161991 is about 544.1945749600.

The spelling of 161161991 in words is "one hundred sixty-one million, one hundred sixty-one thousand, nine hundred ninety-one".