111611561 has 4 divisors (see below), whose sum is σ = 111786324. Its totient is φ = 111436800.

The previous prime is 111611543. The next prime is 111611581. The reversal of 111611561 is 165116111.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165116111 = 29 ⋅5693659.

It can be written as a sum of positive squares in 2 ways, for example, as 66520336 + 45091225 = 8156^2 + 6715^2 .

It is a cyclic number.

It is not a de Polignac number, because 111611561 - 2⁶ = 111611497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (111611581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 86420 + ... + 87701.

It is an arithmetic number, because the mean of its divisors is an integer number (27946581).

Almost surely, 2^111611561 is an apocalyptic number.

It is an amenable number.

111611561 is a deficient number, since it is larger than the sum of its proper divisors (174763).

111611561 is an equidigital number, since it uses as much as digits as its factorization.

111611561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 174762.

The product of its digits is 180, while the sum is 23.

The square root of 111611561 is about 10564.6372867222. The cubic root of 111611561 is about 481.4705494751.

Adding to 111611561 its reverse (165116111), we get a palindrome (276727672).

The spelling of 111611561 in words is "one hundred eleven million, six hundred eleven thousand, five hundred sixty-one".