21982 has 8 divisors (see below), whose sum is σ = 34200. Its totient is φ = 10584.

The previous prime is 21977. The next prime is 21991. The reversal of 21982 is 28912.

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

It is a plaindrome in base 16.

It is a congruent number.

It is an unprimeable number.

21982 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132 + ... + 247.

It is an arithmetic number, because the mean of its divisors is an integer number (4275).

2²¹⁹⁸² is an apocalyptic number.

21982 is a deficient number, since it is larger than the sum of its proper divisors (12218).

21982 is a wasteful number, since it uses less digits than its factorization.

21982 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 410.

The product of its digits is 288, while the sum is 22.

The square root of 21982 is about 148.2632793378. The cubic root of 21982 is about 28.0127492960.

The spelling of 21982 in words is "twenty-one thousand, nine hundred eighty-two".