21642 has 8 divisors (see below), whose sum is σ = 43296. Its totient is φ = 7212.

The previous prime is 21617. The next prime is 21647. The reversal of 21642 is 24612.

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

21642 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21647) by changing a digit.

21642 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, 1798 + ... + 1809.

It is an arithmetic number, because the mean of its divisors is an integer number (5412).

2²¹⁶⁴² is an apocalyptic number.

21642 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21648).

21642 is a wasteful number, since it uses less digits than its factorization.

21642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3612.

The product of its digits is 96, while the sum is 15.

The square root of 21642 is about 147.1122020772. The cubic root of 21642 is about 27.8675719381.

The spelling of 21642 in words is "twenty-one thousand, six hundred forty-two".