21111101221 has 16 divisors (see below), whose sum is σ = 24496940160. Its totient is φ = 17817972480.

The previous prime is 21111101213. The next prime is 21111101239. The reversal of 21111101221 is 12210111112.

It is a happy number.

It is not a de Polignac number, because 21111101221 - 2³ = 21111101213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111101201) 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, 1384881 + ... + 1400041.

It is an arithmetic number, because the mean of its divisors is an integer number (1531058760).

Almost surely, 2^21111101221 is an apocalyptic number.

It is an amenable number.

21111101221 is a deficient number, since it is larger than the sum of its proper divisors (3385838939).

21111101221 is a wasteful number, since it uses less digits than its factorization.

21111101221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18204.

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

Adding to 21111101221 its reverse (12210111112), we get a palindrome (33321212333).

The spelling of 21111101221 in words is "twenty-one billion, one hundred eleven million, one hundred one thousand, two hundred twenty-one".