21312221 has 8 divisors (see below), whose sum is σ = 25142784. Its totient is φ = 17678160.

The previous prime is 21312173. The next prime is 21312223. The reversal of 21312221 is 12221312.

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 21312221 - 2¹⁴ = 21295837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21312196 and 21312205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48890 + ... + 49323.

It is an arithmetic number, because the mean of its divisors is an integer number (3142848).

Almost surely, 2^21312221 is an apocalyptic number.

It is an amenable number.

21312221 is a deficient number, since it is larger than the sum of its proper divisors (3830563).

21312221 is an equidigital number, since it uses as much as digits as its factorization.

21312221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98251.

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

The square root of 21312221 is about 4616.5161106618. The cubic root of 21312221 is about 277.2529890781.

Adding to 21312221 its reverse (12221312), we get a palindrome (33533533).

Subtracting from 21312221 its reverse (12221312), we obtain a palindrome (9090909).

The spelling of 21312221 in words is "twenty-one million, three hundred twelve thousand, two hundred twenty-one".