111781 has 2 divisors, whose sum is σ = 111782. Its totient is φ = 111780.

The previous prime is 111779. The next prime is 111791. The reversal of 111781 is 187111.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 111556 + 225 = 334^2 + 15^2 .

It is an emirp because it is prime and its reverse (187111) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 111781 - 2¹ = 111779 is a prime.

It is a super-2 number, since 2×111781² = 24989983922, which contains 22 as substring.

Together with 111779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (111721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55890 + 55891.

It is an arithmetic number, because the mean of its divisors is an integer number (55891).

2¹¹¹⁷⁸¹ is an apocalyptic number.

It is an amenable number.

111781 is a deficient number, since it is larger than the sum of its proper divisors (1).

111781 is an equidigital number, since it uses as much as digits as its factorization.

111781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 56, while the sum is 19.

The square root of 111781 is about 334.3366566801. The cubic root of 111781 is about 48.1714068575.

Adding to 111781 its reverse (187111), we get a palindrome (298892).

It can be divided in two parts, 11 and 1781, that multiplied together give a palindrome (19591).

The spelling of 111781 in words is "one hundred eleven thousand, seven hundred eighty-one".