21386 has 12 divisors (see below), whose sum is σ = 34998. Its totient is φ = 9792.

The previous prime is 21383. The next prime is 21391. The reversal of 21386 is 68312.

It can be written as a sum of positive squares in 3 ways, for example, as 21025 + 361 = 145^2 + 19^2 .

It is a hoax number, since the sum of its digits (20) coincides with the sum of the digits of its distinct prime factors.

It is an Ulam number.

It is a Curzon number.

It is a nialpdrome in base 13.

It is not an unprimeable number, because it can be changed into a prime (21383) 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 5 ways as a sum of consecutive naturals, for example, 560 + ... + 596.

2²¹³⁸⁶ is an apocalyptic number.

21386 is a deficient number, since it is larger than the sum of its proper divisors (13612).

21386 is a wasteful number, since it uses less digits than its factorization.

With its predecessor (21385) it forms an eRAP, since the sums of their prime factors are consecutive (72 and 73).

21386 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73 (or 56 counting only the distinct ones).

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

The square root of 21386 is about 146.2395295397. The cubic root of 21386 is about 27.7572553601.

Adding to 21386 its reverse (68312), we get a palindrome (89698).

It can be divided in two parts, 2 and 1386, that multiplied together give a palindrome (2772).

The spelling of 21386 in words is "twenty-one thousand, three hundred eighty-six".