21101111221 has 2 divisors, whose sum is σ = 21101111222. Its totient is φ = 21101111220.

The previous prime is 21101111189. The next prime is 21101111243. The reversal of 21101111221 is 12211110112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13685490225 + 7415620996 = 116985^2 + 86114^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101111221 - 2⁵ = 21101111189 is a prime.

It is a super-2 number, since 2×21101111221² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21101111261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550555610 + 10550555611.

It is an arithmetic number, because the mean of its divisors is an integer number (10550555611).

Almost surely, 2^21101111221 is an apocalyptic number.

It is an amenable number.

21101111221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101111221 is an equidigital number, since it uses as much as digits as its factorization.

21101111221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21101111221 its reverse (12211110112), we get a palindrome (33312221333).

The spelling of 21101111221 in words is "twenty-one billion, one hundred one million, one hundred eleven thousand, two hundred twenty-one".