111211121821 has 2 divisors, whose sum is σ = 111211121822. Its totient is φ = 111211121820.

The previous prime is 111211121779. The next prime is 111211121831. The reversal of 111211121821 is 128121112111.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 101323802596 + 9887319225 = 318314^2 + 99435^2 .

It is an emirp because it is prime and its reverse (128121112111) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-111211121821 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 111211121792 and 111211121801.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (111211121831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55605560910 + 55605560911.

It is an arithmetic number, because the mean of its divisors is an integer number (55605560911).

Almost surely, 2^111211121821 is an apocalyptic number.

It is an amenable number.

111211121821 is a deficient number, since it is larger than the sum of its proper divisors (1).

111211121821 is an equidigital number, since it uses as much as digits as its factorization.

111211121821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 64, while the sum is 22.

Adding to 111211121821 its reverse (128121112111), we get a palindrome (239332233932).

The spelling of 111211121821 in words is "one hundred eleven billion, two hundred eleven million, one hundred twenty-one thousand, eight hundred twenty-one".