21499 has 2 divisors, whose sum is σ = 21500. Its totient is φ = 21498.

The previous prime is 21493. The next prime is 21503. The reversal of 21499 is 99412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21499 - 2³ = 21491 is a prime.

21499 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (21491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10749 + 10750.

It is an arithmetic number, because the mean of its divisors is an integer number (10750).

2²¹⁴⁹⁹ is an apocalyptic number.

21499 is a deficient number, since it is larger than the sum of its proper divisors (1).

21499 is an equidigital number, since it uses as much as digits as its factorization.

21499 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 25.

The square root of 21499 is about 146.6253729748. The cubic root of 21499 is about 27.8060577176.

It can be divided in two parts, 214 and 99, that added together give a palindrome (313).

The spelling of 21499 in words is "twenty-one thousand, four hundred ninety-nine".