21221231 has 8 divisors (see below), whose sum is σ = 22246224. Its totient is φ = 20220480.

The previous prime is 21221171. The next prime is 21221237. The reversal of 21221231 is 13212212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21221231 - 2¹⁸ = 20959087 is a prime.

It is a super-2 number, since 2×21221231² = 900681290310722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221237) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4256 + ... + 7781.

It is an arithmetic number, because the mean of its divisors is an integer number (2780778).

Almost surely, 2^21221231 is an apocalyptic number.

21221231 is a deficient number, since it is larger than the sum of its proper divisors (1024993).

21221231 is a wasteful number, since it uses less digits than its factorization.

21221231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12121.

The product of its digits is 48, while the sum is 14.

The square root of 21221231 is about 4606.6507356213. The cubic root of 21221231 is about 276.8578599727.

Adding to 21221231 its reverse (13212212), we get a palindrome (34433443).

The spelling of 21221231 in words is "twenty-one million, two hundred twenty-one thousand, two hundred thirty-one".