21086 has 8 divisors (see below), whose sum is σ = 34104. Its totient is φ = 9720.

The previous prime is 21067. The next prime is 21089. The reversal of 21086 is 68012.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21089) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 380 + ... + 431.

It is an arithmetic number, because the mean of its divisors is an integer number (4263).

2²¹⁰⁸⁶ is an apocalyptic number.

21086 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21086 is a deficient number, since it is larger than the sum of its proper divisors (13018).

21086 is a wasteful number, since it uses less digits than its factorization.

21086 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 826.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 21086 is about 145.2101924797. The cubic root of 21086 is about 27.6268519741.

Adding to 21086 its reverse (68012), we get a palindrome (89098).

The spelling of 21086 in words is "twenty-one thousand, eighty-six".