111821 has 2 divisors, whose sum is σ = 111822. Its totient is φ = 111820.

The previous prime is 111799. The next prime is 111827. The reversal of 111821 is 128111.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 98596 + 13225 = 314^2 + 115^2 .

It is an emirp because it is prime and its reverse (128111) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-111821 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 111796 and 111805.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (111827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55910 + 55911.

It is an arithmetic number, because the mean of its divisors is an integer number (55911).

2¹¹¹⁸²¹ is an apocalyptic number.

It is an amenable number.

111821 is a deficient number, since it is larger than the sum of its proper divisors (1).

111821 is an equidigital number, since it uses as much as digits as its factorization.

111821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16, while the sum is 14.

The square root of 111821 is about 334.3964712732. The cubic root of 111821 is about 48.1771520989.

Adding to 111821 its reverse (128111), we get a palindrome (239932).

Subtracting 111821 from its reverse (128111), we obtain a triangular number (16290 = T₁₈₀).

The spelling of 111821 in words is "one hundred eleven thousand, eight hundred twenty-one".