21842521 has 2 divisors, whose sum is σ = 21842522. Its totient is φ = 21842520.

The previous prime is 21842497. The next prime is 21842551. The reversal of 21842521 is 12524812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18156121 + 3686400 = 4261^2 + 1920^2 .

It is a cyclic number.

It is not a de Polignac number, because 21842521 - 2⁷ = 21842393 is a prime.

It is not a weakly prime, because it can be changed into another prime (21842551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10921260 + 10921261.

It is an arithmetic number, because the mean of its divisors is an integer number (10921261).

Almost surely, 2^21842521 is an apocalyptic number.

It is an amenable number.

21842521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21842521 is an equidigital number, since it uses as much as digits as its factorization.

21842521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1280, while the sum is 25.

The square root of 21842521 is about 4673.5982925365. The cubic root of 21842521 is about 279.5337521097.

The spelling of 21842521 in words is "twenty-one million, eight hundred forty-two thousand, five hundred twenty-one".