21686223 has 16 divisors (see below), whose sum is σ = 31804416. Its totient is φ = 13060320.

The previous prime is 21686221. The next prime is 21686227. The reversal of 21686223 is 32268612.

It is not a de Polignac number, because 21686223 - 2¹ = 21686221 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21686221) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4083 + ... + 7748.

It is an arithmetic number, because the mean of its divisors is an integer number (1987776).

Almost surely, 2^21686223 is an apocalyptic number.

21686223 is a deficient number, since it is larger than the sum of its proper divisors (10118193).

21686223 is a wasteful number, since it uses less digits than its factorization.

21686223 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11894.

The product of its digits is 6912, while the sum is 30.

The square root of 21686223 is about 4656.8468946273. The cubic root of 21686223 is about 278.8654044329.

The spelling of 21686223 in words is "twenty-one million, six hundred eighty-six thousand, two hundred twenty-three".