21111221221 has 4 divisors (see below), whose sum is σ = 21112531200. Its totient is φ = 21109911244.

The previous prime is 21111221213. The next prime is 21111221227. The reversal of 21111221221 is 12212211112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21111221221 - 2³ = 21111221213 is a prime.

It is a super-2 number, since 2×21111221221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21111221195 and 21111221204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111221227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 630511 + ... + 663148.

It is an arithmetic number, because the mean of its divisors is an integer number (5278132800).

Almost surely, 2^21111221221 is an apocalyptic number.

It is an amenable number.

21111221221 is a deficient number, since it is larger than the sum of its proper divisors (1309979).

21111221221 is a wasteful number, since it uses less digits than its factorization.

21111221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1309978.

The product of its digits is 32, while the sum is 16.

Adding to 21111221221 its reverse (12212211112), we get a palindrome (33323432333).

The spelling of 21111221221 in words is "twenty-one billion, one hundred eleven million, two hundred twenty-one thousand, two hundred twenty-one".