21686423 has 8 divisors (see below), whose sum is σ = 23779200. Its totient is φ = 19613880.

The previous prime is 21686419. The next prime is 21686443. The reversal of 21686423 is 32468612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21686423 - 2² = 21686419 is a prime.

It is a super-3 number, since 3×21686423³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21686423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21686443) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2765 + ... + 7142.

It is an arithmetic number, because the mean of its divisors is an integer number (2972400).

Almost surely, 2^21686423 is an apocalyptic number.

21686423 is a deficient number, since it is larger than the sum of its proper divisors (2092777).

21686423 is a wasteful number, since it uses less digits than its factorization.

21686423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10117.

The product of its digits is 13824, while the sum is 32.

The square root of 21686423 is about 4656.8683683351. The cubic root of 21686423 is about 278.8662617038.

The spelling of 21686423 in words is "twenty-one million, six hundred eighty-six thousand, four hundred twenty-three".