21457253 has 2 divisors, whose sum is σ = 21457254. Its totient is φ = 21457252.

The previous prime is 21457207. The next prime is 21457279. The reversal of 21457253 is 35275412.

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., 14577124 + 6880129 = 3818^2 + 2623^2 .

It is a cyclic number.

It is not a de Polignac number, because 21457253 - 2²⁰ = 20408677 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21457153) 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, 10728626 + 10728627.

It is an arithmetic number, because the mean of its divisors is an integer number (10728627).

Almost surely, 2^21457253 is an apocalyptic number.

It is an amenable number.

21457253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21457253 is an equidigital number, since it uses as much as digits as its factorization.

21457253 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8400, while the sum is 29.

The square root of 21457253 is about 4632.1974267080. The cubic root of 21457253 is about 277.8804801685.

The spelling of 21457253 in words is "twenty-one million, four hundred fifty-seven thousand, two hundred fifty-three".