21111112222221 has 16 divisors (see below), whose sum is σ = 32169706569728. Its totient is φ = 12063345433200.

The previous prime is 21111112222169. The next prime is 21111112222241. The reversal of 21111112222221 is 12222221111112.

It is not a de Polignac number, because 21111112222221 - 2⁷ = 21111112222093 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111112222241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4362925 + ... + 7826706.

It is an arithmetic number, because the mean of its divisors is an integer number (2010606660608).

Almost surely, 2^{21111112222221} is an apocalyptic number.

21111112222221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21111112222221 is a deficient number, since it is larger than the sum of its proper divisors (11058594347507).

21111112222221 is a wasteful number, since it uses less digits than its factorization.

21111112222221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12272112.

The product of its digits is 128, while the sum is 21.

Adding to 21111112222221 its reverse (12222221111112), we get a palindrome (33333333333333).

The spelling of 21111112222221 in words is "twenty-one trillion, one hundred eleven billion, one hundred twelve million, two hundred twenty-two thousand, two hundred twenty-one".