161811813 has 4 divisors (see below), whose sum is σ = 215749088. Its totient is φ = 107874540.

The previous prime is 161811803. The next prime is 161811817. The reversal of 161811813 is 318118161.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 161811813 - 2⁵ = 161811781 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161811817) 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 3 ways as a sum of consecutive naturals, for example, 26968633 + ... + 26968638.

It is an arithmetic number, because the mean of its divisors is an integer number (53937272).

Almost surely, 2^161811813 is an apocalyptic number.

It is an amenable number.

161811813 is a deficient number, since it is larger than the sum of its proper divisors (53937275).

161811813 is an equidigital number, since it uses as much as digits as its factorization.

161811813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53937274.

The product of its digits is 1152, while the sum is 30.

The square root of 161811813 is about 12720.5272296395. The cubic root of 161811813 is about 544.9250105840.

Adding to 161811813 its reverse (318118161), we get a palindrome (479929974).

It can be divided in two parts, 1618 and 11813, that added together give a palindrome (13431).

The spelling of 161811813 in words is "one hundred sixty-one million, eight hundred eleven thousand, eight hundred thirteen".