21221111 has 16 divisors (see below), whose sum is σ = 23030784. Its totient is φ = 19503264.

The previous prime is 21221099. The next prime is 21221113. The reversal of 21221111 is 11112212.

It is not a de Polignac number, because 21221111 - 2⁶ = 21221047 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21221092 and 21221101.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221113) 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, 72281 + ... + 72573.

It is an arithmetic number, because the mean of its divisors is an integer number (1439424).

Almost surely, 2^21221111 is an apocalyptic number.

21221111 is a deficient number, since it is larger than the sum of its proper divisors (1809673).

21221111 is a wasteful number, since it uses less digits than its factorization.

21221111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 430.

The product of its digits is 8, while the sum is 11.

The square root of 21221111 is about 4606.6377109558. The cubic root of 21221111 is about 276.8573381210.

Adding to 21221111 its reverse (11112212), we get a palindrome (32333323).

The spelling of 21221111 in words is "twenty-one million, two hundred twenty-one thousand, one hundred eleven".