21513523 has 2 divisors, whose sum is σ = 21513524. Its totient is φ = 21513522.

The previous prime is 21513511. The next prime is 21513559. The reversal of 21513523 is 32531512.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21513523 is a prime.

It is a zygodrome in base 3.

It is a junction number, because it is equal to n+sod(n) for n = 21513494 and 21513503.

It is not a weakly prime, because it can be changed into another prime (21513593) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756761 + 10756762.

It is an arithmetic number, because the mean of its divisors is an integer number (10756762).

Almost surely, 2^21513523 is an apocalyptic number.

21513523 is a deficient number, since it is larger than the sum of its proper divisors (1).

21513523 is an equidigital number, since it uses as much as digits as its factorization.

21513523 is an evil number, because the sum of its binary digits is even.

The product of its digits is 900, while the sum is 22.

The square root of 21513523 is about 4638.2672411149. The cubic root of 21513523 is about 278.1231748902.

The spelling of 21513523 in words is "twenty-one million, five hundred thirteen thousand, five hundred twenty-three".