21057523 has 2 divisors, whose sum is σ = 21057524. Its totient is φ = 21057522.

The previous prime is 21057521. The next prime is 21057541. The reversal of 21057523 is 32575012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21057523 - 2¹ = 21057521 is a prime.

Together with 21057521, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21057521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10528761 + 10528762.

It is an arithmetic number, because the mean of its divisors is an integer number (10528762).

Almost surely, 2^21057523 is an apocalyptic number.

21057523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21057523 is an equidigital number, since it uses as much as digits as its factorization.

21057523 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2100, while the sum is 25.

The square root of 21057523 is about 4588.8476767049. The cubic root of 21057523 is about 276.1440952744.

The spelling of 21057523 in words is "twenty-one million, fifty-seven thousand, five hundred twenty-three".