21231217 has 16 divisors (see below), whose sum is σ = 25038720. Its totient is φ = 17626752.

The previous prime is 21231173. The next prime is 21231241. The reversal of 21231217 is 71213212.

It is a cyclic number.

It is not a de Polignac number, because 21231217 - 2¹⁹ = 20706929 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21231194 and 21231203.

It is not an unprimeable number, because it can be changed into a prime (21237217) 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, 32698 + ... + 33340.

It is an arithmetic number, because the mean of its divisors is an integer number (1564920).

Almost surely, 2^21231217 is an apocalyptic number.

It is an amenable number.

21231217 is a deficient number, since it is larger than the sum of its proper divisors (3807503).

21231217 is an equidigital number, since it uses as much as digits as its factorization.

21231217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 792.

The product of its digits is 168, while the sum is 19.

The square root of 21231217 is about 4607.7344758569. The cubic root of 21231217 is about 276.9012798390.

Adding to 21231217 its reverse (71213212), we get a palindrome (92444429).

The spelling of 21231217 in words is "twenty-one million, two hundred thirty-one thousand, two hundred seventeen".