161991436 has 24 divisors (see below), whose sum is σ = 301235760. Its totient is φ = 76222016.

The previous prime is 161991433. The next prime is 161991443. The reversal of 161991436 is 634199161.

It is a happy number.

161991436 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (161991433) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15531 + ... + 23773.

It is an arithmetic number, because the mean of its divisors is an integer number (12551490).

Almost surely, 2^161991436 is an apocalyptic number.

It is an amenable number.

161991436 is a deficient number, since it is larger than the sum of its proper divisors (139244324).

161991436 is an equidigital number, since it uses as much as digits as its factorization.

161991436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8298 (or 8262 counting only the distinct ones).

The product of its digits is 34992, while the sum is 40.

The square root of 161991436 is about 12727.5856312185. The cubic root of 161991436 is about 545.1265716182.

The spelling of 161991436 in words is "one hundred sixty-one million, nine hundred ninety-one thousand, four hundred thirty-six".