21424253 has 2 divisors, whose sum is σ = 21424254. Its totient is φ = 21424252.

The previous prime is 21424241. The next prime is 21424261. The reversal of 21424253 is 35242412.

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., 16216729 + 5207524 = 4027^2 + 2282^2 .

It is a cyclic number.

It is not a de Polignac number, because 21424253 - 2⁶ = 21424189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21424213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10712126 + 10712127.

It is an arithmetic number, because the mean of its divisors is an integer number (10712127).

Almost surely, 2^21424253 is an apocalyptic number.

It is an amenable number.

21424253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21424253 is an equidigital number, since it uses as much as digits as its factorization.

21424253 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1920, while the sum is 23.

The square root of 21424253 is about 4628.6340317636. The cubic root of 21424253 is about 277.7379524356.

Adding to 21424253 its reverse (35242412), we get a palindrome (56666665).

The spelling of 21424253 in words is "twenty-one million, four hundred twenty-four thousand, two hundred fifty-three".