21013217 has 2 divisors, whose sum is σ = 21013218. Its totient is φ = 21013216.

The previous prime is 21013189. The next prime is 21013249. The reversal of 21013217 is 71231012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20939776 + 73441 = 4576^2 + 271^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013217 - 2¹⁰ = 21012193 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21013195 and 21013204.

It is not a weakly prime, because it can be changed into another prime (21013117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10506608 + 10506609.

It is an arithmetic number, because the mean of its divisors is an integer number (10506609).

Almost surely, 2^21013217 is an apocalyptic number.

It is an amenable number.

21013217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21013217 is an equidigital number, since it uses as much as digits as its factorization.

21013217 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21013217 is about 4584.0175610484. The cubic root of 21013217 is about 275.9502859769.

Adding to 21013217 its reverse (71231012), we get a palindrome (92244229).

The spelling of 21013217 in words is "twenty-one million, thirteen thousand, two hundred seventeen".