21211217 has 2 divisors, whose sum is σ = 21211218. Its totient is φ = 21211216.

The previous prime is 21211181. The next prime is 21211237. The reversal of 21211217 is 71211212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20939776 + 271441 = 4576^2 + 521^2 .

It is a cyclic number.

It is not a de Polignac number, because 21211217 - 2⁸ = 21210961 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21211195 and 21211204.

It is not a weakly prime, because it can be changed into another prime (21211237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605608 + 10605609.

It is an arithmetic number, because the mean of its divisors is an integer number (10605609).

Almost surely, 2^21211217 is an apocalyptic number.

It is an amenable number.

21211217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21211217 is an equidigital number, since it uses as much as digits as its factorization.

21211217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56, while the sum is 17.

The square root of 21211217 is about 4605.5637005691. The cubic root of 21211217 is about 276.8143046794.

Adding to 21211217 its reverse (71211212), we get a palindrome (92422429).

The spelling of 21211217 in words is "twenty-one million, two hundred eleven thousand, two hundred seventeen".