21983 has 8 divisors (see below), whose sum is σ = 25200. Its totient is φ = 19008.

The previous prime is 21977. The next prime is 21991. The reversal of 21983 is 38912.

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

It is a cyclic number.

It is not a de Polignac number, because 21983 - 2⁸ = 21727 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 203 + ... + 291.

It is an arithmetic number, because the mean of its divisors is an integer number (3150).

2²¹⁹⁸³ is an apocalyptic number.

21983 is a deficient number, since it is larger than the sum of its proper divisors (3217).

21983 is a wasteful number, since it uses less digits than its factorization.

21983 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121.

The product of its digits is 432, while the sum is 23.

The square root of 21983 is about 148.2666516787. The cubic root of 21983 is about 28.0131740727.

The spelling of 21983 in words is "twenty-one thousand, nine hundred eighty-three".