161499991 has 2 divisors, whose sum is σ = 161499992. Its totient is φ = 161499990.

The previous prime is 161499979. The next prime is 161500013. The reversal of 161499991 is 199994161.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 161499991 - 2²¹ = 159402839 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161499901) 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 as a sum of consecutive naturals, namely, 80749995 + 80749996.

It is an arithmetic number, because the mean of its divisors is an integer number (80749996).

Almost surely, 2^161499991 is an apocalyptic number.

161499991 is a deficient number, since it is larger than the sum of its proper divisors (1).

161499991 is an equidigital number, since it uses as much as digits as its factorization.

161499991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 157464, while the sum is 49.

The square root of 161499991 is about 12708.2646730386. The cubic root of 161499991 is about 544.5747500576.

The spelling of 161499991 in words is "one hundred sixty-one million, four hundred ninety-nine thousand, nine hundred ninety-one".