21836 has 12 divisors (see below), whose sum is σ = 39312. Its totient is φ = 10608.

The previous prime is 21821. The next prime is 21839. The reversal of 21836 is 63812.

21836 is nontrivially palindromic in base 11.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (21839) by changing a digit.

21836 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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, 161 + ... + 263.

It is an arithmetic number, because the mean of its divisors is an integer number (3276).

2²¹⁸³⁶ is an apocalyptic number.

It is an amenable number.

21836 is a deficient number, since it is larger than the sum of its proper divisors (17476).

21836 is a wasteful number, since it uses less digits than its factorization.

21836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160 (or 158 counting only the distinct ones).

The product of its digits is 288, while the sum is 20.

The square root of 21836 is about 147.7700916965. The cubic root of 21836 is about 27.9505931435.

The spelling of 21836 in words is "twenty-one thousand, eight hundred thirty-six".