111781561 has 2 divisors, whose sum is σ = 111781562. Its totient is φ = 111781560.

The previous prime is 111781529. The next prime is 111781583. The reversal of 111781561 is 165187111.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 102515625 + 9265936 = 10125^2 + 3044^2 .

It is an emirp because it is prime and its reverse (165187111) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 111781561 - 2⁵ = 111781529 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (111781591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55890780 + 55890781.

It is an arithmetic number, because the mean of its divisors is an integer number (55890781).

Almost surely, 2^111781561 is an apocalyptic number.

It is an amenable number.

111781561 is a deficient number, since it is larger than the sum of its proper divisors (1).

111781561 is an equidigital number, since it uses as much as digits as its factorization.

111781561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 31.

The square root of 111781561 is about 10572.6799346240. The cubic root of 111781561 is about 481.7148744402.

The spelling of 111781561 in words is "one hundred eleven million, seven hundred eighty-one thousand, five hundred sixty-one".