111666561 has 4 divisors (see below), whose sum is σ = 148888752. Its totient is φ = 74444372.

The previous prime is 111666551. The next prime is 111666563. The reversal of 111666561 is 165666111.

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 a cyclic number.

It is not a de Polignac number, because 111666561 - 2¹¹ = 111664513 is a prime.

It is not an unprimeable number, because it can be changed into a prime (111666563) 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, 18611091 + ... + 18611096.

It is an arithmetic number, because the mean of its divisors is an integer number (37222188).

Almost surely, 2^111666561 is an apocalyptic number.

It is an amenable number.

111666561 is a deficient number, since it is larger than the sum of its proper divisors (37222191).

111666561 is an equidigital number, since it uses as much as digits as its factorization.

111666561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37222190.

The product of its digits is 6480, while the sum is 33.

The square root of 111666561 is about 10567.2399897040. The cubic root of 111666561 is about 481.5496229195.

It can be divided in two parts, 111666 and 561, that multiplied together give a palindrome (62644626).

The spelling of 111666561 in words is "one hundred eleven million, six hundred sixty-six thousand, five hundred sixty-one".