21863 has 2 divisors, whose sum is σ = 21864. Its totient is φ = 21862.

The previous prime is 21859. The next prime is 21871. The reversal of 21863 is 36812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21863 - 2² = 21859 is a prime.

It is a Chen prime.

It is an Ulam number.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21803) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10931 + 10932.

It is an arithmetic number, because the mean of its divisors is an integer number (10932).

2²¹⁸⁶³ is an apocalyptic number.

21863 is a deficient number, since it is larger than the sum of its proper divisors (1).

21863 is an equidigital number, since it uses as much as digits as its factorization.

21863 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21863 is about 147.8614216082. The cubic root of 21863 is about 27.9621086100.

The spelling of 21863 in words is "twenty-one thousand, eight hundred sixty-three".