21704523 has 4 divisors (see below), whose sum is σ = 28939368. Its totient is φ = 14469680.

The previous prime is 21704521. The next prime is 21704531. The reversal of 21704523 is 32540712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21704523 - 2¹ = 21704521 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21704493 and 21704502.

It is not an unprimeable number, because it can be changed into a prime (21704521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3617418 + ... + 3617423.

It is an arithmetic number, because the mean of its divisors is an integer number (7234842).

Almost surely, 2^21704523 is an apocalyptic number.

21704523 is a deficient number, since it is larger than the sum of its proper divisors (7234845).

21704523 is an equidigital number, since it uses as much as digits as its factorization.

21704523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7234844.

The product of its (nonzero) digits is 1680, while the sum is 24.

The square root of 21704523 is about 4658.8113290838. The cubic root of 21704523 is about 278.9438229156.

The spelling of 21704523 in words is "twenty-one million, seven hundred four thousand, five hundred twenty-three".