21224321 has 2 divisors, whose sum is σ = 21224322. Its totient is φ = 21224320.

The previous prime is 21224297. The next prime is 21224323. The reversal of 21224321 is 12342212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20295025 + 929296 = 4505^2 + 964^2 .

It is a cyclic number.

It is not a de Polignac number, because 21224321 - 2¹⁰ = 21223297 is a prime.

It is a super-2 number, since 2×21224321² = 900943603822082, which contains 22 as substring.

Together with 21224323, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21224321.

It is not a weakly prime, because it can be changed into another prime (21224323) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10612160 + 10612161.

It is an arithmetic number, because the mean of its divisors is an integer number (10612161).

Almost surely, 2^21224321 is an apocalyptic number.

It is an amenable number.

21224321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21224321 is an equidigital number, since it uses as much as digits as its factorization.

21224321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 192, while the sum is 17.

The square root of 21224321 is about 4606.9861080754. The cubic root of 21224321 is about 276.8712969762.

Adding to 21224321 its reverse (12342212), we get a palindrome (33566533).

The spelling of 21224321 in words is "twenty-one million, two hundred twenty-four thousand, three hundred twenty-one".