21723 has 8 divisors (see below), whose sum is σ = 31248.
Its totient is φ = 13344.
The previous prime is 21713. The next prime is 21727. The reversal of 21723 is 32712.
It is a sphenic number, since it is the product of 3 distinct primes.
It is not a de Polignac number, because 21723 - 28 = 21467 is a prime.
It is not an unprimeable number, because it can be changed into a prime (21727) by changing a digit.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 240 + ... + 317.
It is an arithmetic number, because the mean of its divisors is an integer number (3906).
221723 is an apocalyptic number.
21723 is a deficient number, since it is larger than the sum of its proper divisors (9525).
21723 is a wasteful number, since it uses less digits than its factorization.
21723 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 573.
The product of its digits is 84, while the sum is 15.
The square root of 21723 is about 147.3872450384.
The cubic root of 21723 is about 27.9022955165.
The spelling of 21723 in words is "twenty-one thousand, seven hundred twenty-three", and thus it is an iban number.