21224657 has 2 divisors, whose sum is σ = 21224658. Its totient is φ = 21224656.

The previous prime is 21224647. The next prime is 21224659. The reversal of 21224657 is 75642212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16008001 + 5216656 = 4001^2 + 2284^2 .

It is a cyclic number.

It is not a de Polignac number, because 21224657 - 2¹⁶ = 21159121 is a prime.

Together with 21224659, 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 (21224659) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10612328 + 10612329.

It is an arithmetic number, because the mean of its divisors is an integer number (10612329).

Almost surely, 2^21224657 is an apocalyptic number.

It is an amenable number.

21224657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21224657 is an equidigital number, since it uses as much as digits as its factorization.

21224657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6720, while the sum is 29.

The square root of 21224657 is about 4607.0225742881. The cubic root of 21224657 is about 276.8727580086.

Adding to 21224657 its reverse (75642212), we get a palindrome (96866869).

The spelling of 21224657 in words is "twenty-one million, two hundred twenty-four thousand, six hundred fifty-seven".