111978561 has 4 divisors (see below), whose sum is σ = 149304752. Its totient is φ = 74652372.

The previous prime is 111978551. The next prime is 111978583. The reversal of 111978561 is 165879111.

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, and also an emirpimes, since its reverse is a distinct semiprime: 165879111 = 3 ⋅55293037.

It is not a de Polignac number, because 111978561 - 2⁹ = 111978049 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (111978521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18663091 + ... + 18663096.

It is an arithmetic number, because the mean of its divisors is an integer number (37326188).

Almost surely, 2^111978561 is an apocalyptic number.

It is an amenable number.

111978561 is a deficient number, since it is larger than the sum of its proper divisors (37326191).

111978561 is an equidigital number, since it uses as much as digits as its factorization.

111978561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37326190.

The product of its digits is 15120, while the sum is 39.

The square root of 111978561 is about 10581.9922982395. The cubic root of 111978561 is about 481.9976943009.

The spelling of 111978561 in words is "one hundred eleven million, nine hundred seventy-eight thousand, five hundred sixty-one".