21221220111 has 16 divisors (see below), whose sum is σ = 34824566784. Its totient is φ = 11193610464.

The previous prime is 21221220109. The next prime is 21221220151. The reversal of 21221220111 is 11102212212.

It is not a de Polignac number, because 21221220111 - 2¹ = 21221220109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221220101) 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, 38866431 + ... + 38866976.

It is an arithmetic number, because the mean of its divisors is an integer number (2176535424).

Almost surely, 2^21221220111 is an apocalyptic number.

21221220111 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21221220111 is a deficient number, since it is larger than the sum of its proper divisors (13603346673).

21221220111 is a wasteful number, since it uses less digits than its factorization.

21221220111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77733430.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21221220111 its reverse (11102212212), we get a palindrome (32323432323).

It can be divided in two parts, 212212201 and 11, that added together give a palindrome (212212212).

The spelling of 21221220111 in words is "twenty-one billion, two hundred twenty-one million, two hundred twenty thousand, one hundred eleven".