20111221 has 24 divisors (see below), whose sum is σ = 23673384. Its totient is φ = 16972800.

The previous prime is 20111213. The next prime is 20111243. The reversal of 20111221 is 12211102.

It can be written as a sum of positive squares in 12 ways, for example, as 264196 + 19847025 = 514^2 + 4455^2 .

It is not a de Polignac number, because 20111221 - 2³ = 20111213 is a prime.

It is a super-2 number, since 2×20111221² = 808922420221682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20111198 and 20111207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20111261) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 199071 + ... + 199171.

It is an arithmetic number, because the mean of its divisors is an integer number (986391).

Almost surely, 2^20111221 is an apocalyptic number.

It is an amenable number.

20111221 is a deficient number, since it is larger than the sum of its proper divisors (3562163).

20111221 is a wasteful number, since it uses less digits than its factorization.

20111221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201 (or 184 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 10.

The square root of 20111221 is about 4484.5536009730. The cubic root of 20111221 is about 271.9439988876.

Adding to 20111221 its reverse (12211102), we get a palindrome (32322323).

The spelling of 20111221 in words is "twenty million, one hundred eleven thousand, two hundred twenty-one".