21803 has 2 divisors, whose sum is σ = 21804. Its totient is φ = 21802.

The previous prime is 21799. The next prime is 21817. The reversal of 21803 is 30812.

It is an a-pointer prime, because the next prime (21817) can be obtained adding 21803 to its sum of digits (14).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21803 - 2² = 21799 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10901 + 10902.

It is an arithmetic number, because the mean of its divisors is an integer number (10902).

2²¹⁸⁰³ is an apocalyptic number.

21803 is a deficient number, since it is larger than the sum of its proper divisors (1).

21803 is an equidigital number, since it uses as much as digits as its factorization.

21803 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21803 is about 147.6583895348. The cubic root of 21803 is about 27.9365057860.

Subtracting 21803 from its reverse (30812), we obtain a palindrome (9009).

The spelling of 21803 in words is "twenty-one thousand, eight hundred three".