21321217 has 2 divisors, whose sum is σ = 21321218. Its totient is φ = 21321216.

The previous prime is 21321203. The next prime is 21321263. The reversal of 21321217 is 71212312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18113536 + 3207681 = 4256^2 + 1791^2 .

It is a cyclic number.

It is not a de Polignac number, because 21321217 - 2⁷ = 21321089 is a prime.

It is a super-2 number, since 2×21321217² = 909188588722178, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21321194 and 21321203.

It is not a weakly prime, because it can be changed into another prime (21321277) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660608 + 10660609.

It is an arithmetic number, because the mean of its divisors is an integer number (10660609).

Almost surely, 2^21321217 is an apocalyptic number.

It is an amenable number.

21321217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21321217 is an equidigital number, since it uses as much as digits as its factorization.

21321217 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21321217 is about 4617.4903356694. The cubic root of 21321217 is about 277.2919935698.

Adding to 21321217 its reverse (71212312), we get a palindrome (92533529).

The spelling of 21321217 in words is "twenty-one million, three hundred twenty-one thousand, two hundred seventeen".