111809821 has 2 divisors, whose sum is σ = 111809822. Its totient is φ = 111809820.

The previous prime is 111809809. The next prime is 111809827. The reversal of 111809821 is 128908111.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 110544196 + 1265625 = 10514^2 + 1125^2 .

It is a cyclic number.

It is not a de Polignac number, because 111809821 - 2²⁵ = 78255389 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (111809827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55904910 + 55904911.

It is an arithmetic number, because the mean of its divisors is an integer number (55904911).

Almost surely, 2^111809821 is an apocalyptic number.

It is an amenable number.

111809821 is a deficient number, since it is larger than the sum of its proper divisors (1).

111809821 is an equidigital number, since it uses as much as digits as its factorization.

111809821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1152, while the sum is 31.

The square root of 111809821 is about 10574.0163135868. The cubic root of 111809821 is about 481.7554658555.

The spelling of 111809821 in words is "one hundred eleven million, eight hundred nine thousand, eight hundred twenty-one".