21299 has 6 divisors (see below), whose sum is σ = 22860. Its totient is φ = 19836.

The previous prime is 21283. The next prime is 21313. The reversal of 21299 is 99212.

It is not a de Polignac number, because 21299 - 2⁴ = 21283 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21269) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 332 + ... + 390.

It is an arithmetic number, because the mean of its divisors is an integer number (3810).

2²¹²⁹⁹ is an apocalyptic number.

21299 is a deficient number, since it is larger than the sum of its proper divisors (1561).

21299 is an equidigital number, since it uses as much as digits as its factorization.

21299 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97 (or 78 counting only the distinct ones).

The product of its digits is 324, while the sum is 23.

The square root of 21299 is about 145.9417692095. The cubic root of 21299 is about 27.7195646079.

The spelling of 21299 in words is "twenty-one thousand, two hundred ninety-nine".