21708823 has 4 divisors (see below), whose sum is σ = 21765888. Its totient is φ = 21651760.

The previous prime is 21708821. The next prime is 21708857. The reversal of 21708823 is 32880712.

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 21708823 - 2¹ = 21708821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21708821) 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, 27958 + ... + 28723.

It is an arithmetic number, because the mean of its divisors is an integer number (5441472).

Almost surely, 2^21708823 is an apocalyptic number.

21708823 is a deficient number, since it is larger than the sum of its proper divisors (57065).

21708823 is an equidigital number, since it uses as much as digits as its factorization.

21708823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57064.

The product of its (nonzero) digits is 5376, while the sum is 31.

The square root of 21708823 is about 4659.2727973365. The cubic root of 21708823 is about 278.9622427205.

The spelling of 21708823 in words is "twenty-one million, seven hundred eight thousand, eight hundred twenty-three".