211311111821 has 2 divisors, whose sum is σ = 211311111822. Its totient is φ = 211311111820.

The previous prime is 211311111763. The next prime is 211311111917. The reversal of 211311111821 is 128111113112.

It is a m-pointer prime, because the next prime (211311111917) can be obtained adding 211311111821 to its product of digits (96).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 208196913796 + 3114198025 = 456286^2 + 55805^2 .

It is a cyclic number.

It is not a de Polignac number, because 211311111821 - 2⁶ = 211311111757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (211311111521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 105655555910 + 105655555911.

It is an arithmetic number, because the mean of its divisors is an integer number (105655555911).

Almost surely, 2^211311111821 is an apocalyptic number.

It is an amenable number.

211311111821 is a deficient number, since it is larger than the sum of its proper divisors (1).

211311111821 is an equidigital number, since it uses as much as digits as its factorization.

211311111821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 96, while the sum is 23.

Adding to 211311111821 its reverse (128111113112), we get a palindrome (339422224933).

The spelling of 211311111821 in words is "two hundred eleven billion, three hundred eleven million, one hundred eleven thousand, eight hundred twenty-one".