21842 has 8 divisors (see below), whose sum is σ = 33456. Its totient is φ = 10692.

The previous prime is 21841. The next prime is 21851. The reversal of 21842 is 24812.

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

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21842.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21842.

It is not an unprimeable number, because it can be changed into a prime (21841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 53 + ... + 215.

It is an arithmetic number, because the mean of its divisors is an integer number (4182).

2²¹⁸⁴² is an apocalyptic number.

21842 is a deficient number, since it is larger than the sum of its proper divisors (11614).

21842 is a wasteful number, since it uses less digits than its factorization.

21842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 232.

The product of its digits is 128, while the sum is 17.

The square root of 21842 is about 147.7903921099. The cubic root of 21842 is about 27.9531529560.

The spelling of 21842 in words is "twenty-one thousand, eight hundred forty-two".