111664561 has 2 divisors, whose sum is σ = 111664562. Its totient is φ = 111664560.

The previous prime is 111664549. The next prime is 111664571. The reversal of 111664561 is 165466111.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 87310336 + 24354225 = 9344^2 + 4935^2 .

It is an emirp because it is prime and its reverse (165466111) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 111664561 - 2²⁵ = 78110129 is a prime.

It is not a weakly prime, because it can be changed into another prime (111664541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55832280 + 55832281.

It is an arithmetic number, because the mean of its divisors is an integer number (55832281).

Almost surely, 2^111664561 is an apocalyptic number.

It is an amenable number.

111664561 is a deficient number, since it is larger than the sum of its proper divisors (1).

111664561 is an equidigital number, since it uses as much as digits as its factorization.

111664561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 111664561 is about 10567.1453571908. The cubic root of 111664561 is about 481.5467479764.

It can be divided in two parts, 111664 and 561, that added together give a square (112225 = 335²).

The spelling of 111664561 in words is "one hundred eleven million, six hundred sixty-four thousand, five hundred sixty-one".