21662321 has 2 divisors, whose sum is σ = 21662322. Its totient is φ = 21662320.

The previous prime is 21662293. The next prime is 21662323. The reversal of 21662321 is 12326612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16321600 + 5340721 = 4040^2 + 2311^2 .

It is a cyclic number.

It is not a de Polignac number, because 21662321 - 2¹⁴ = 21645937 is a prime.

It is a super-2 number, since 2×21662321² = 938512302214082, which contains 22 as substring.

Together with 21662323, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21662323) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831160 + 10831161.

It is an arithmetic number, because the mean of its divisors is an integer number (10831161).

Almost surely, 2^21662321 is an apocalyptic number.

It is an amenable number.

21662321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21662321 is an equidigital number, since it uses as much as digits as its factorization.

21662321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 864, while the sum is 23.

The square root of 21662321 is about 4654.2798583669. The cubic root of 21662321 is about 278.7629139988.

Adding to 21662321 its reverse (12326612), we get a palindrome (33988933).

The spelling of 21662321 in words is "twenty-one million, six hundred sixty-two thousand, three hundred twenty-one".