161733991 has 2 divisors, whose sum is σ = 161733992. Its totient is φ = 161733990.

The previous prime is 161733977. The next prime is 161734063. The reversal of 161733991 is 199337161.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161733991 - 2⁵ = 161733959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161733941) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80866995 + 80866996.

It is an arithmetic number, because the mean of its divisors is an integer number (80866996).

Almost surely, 2^161733991 is an apocalyptic number.

161733991 is a deficient number, since it is larger than the sum of its proper divisors (1).

161733991 is an equidigital number, since it uses as much as digits as its factorization.

161733991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 30618, while the sum is 40.

The square root of 161733991 is about 12717.4679476695. The cubic root of 161733991 is about 544.8376375761.

It can be divided in two parts, 16173 and 3991, that added together give a square (20164 = 142²).

The spelling of 161733991 in words is "one hundred sixty-one million, seven hundred thirty-three thousand, nine hundred ninety-one".