111551561 has 4 divisors (see below), whose sum is σ = 121692624. Its totient is φ = 101410500.

The previous prime is 111551537. The next prime is 111551599. The reversal of 111551561 is 165155111.

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 a de Polignac number, because none of the positive numbers 2^k-111551561 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 111551561.

It is not an unprimeable number, because it can be changed into a prime (111551521) 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, 5070515 + ... + 5070536.

It is an arithmetic number, because the mean of its divisors is an integer number (30423156).

Almost surely, 2^111551561 is an apocalyptic number.

111551561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

111551561 is a deficient number, since it is larger than the sum of its proper divisors (10141063).

111551561 is a wasteful number, since it uses less digits than its factorization.

111551561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10141062.

The product of its digits is 750, while the sum is 26.

The square root of 111551561 is about 10561.7972428938. The cubic root of 111551561 is about 481.3842579034.

The spelling of 111551561 in words is "one hundred eleven million, five hundred fifty-one thousand, five hundred sixty-one".