21245 has 8 divisors (see below), whose sum is σ = 29184. Its totient is φ = 14544.

The previous prime is 21227. The next prime is 21247. The reversal of 21245 is 54212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21245 - 2¹⁴ = 4861 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21247) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 269 + ... + 338.

It is an arithmetic number, because the mean of its divisors is an integer number (3648).

2²¹²⁴⁵ is an apocalyptic number.

It is an amenable number.

21245 is a deficient number, since it is larger than the sum of its proper divisors (7939).

21245 is an equidigital number, since it uses as much as digits as its factorization.

21245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 619.

The product of its digits is 80, while the sum is 14.

The square root of 21245 is about 145.7566465037. The cubic root of 21245 is about 27.6961186984.

Adding to 21245 its reverse (54212), we get a palindrome (75457).

The spelling of 21245 in words is "twenty-one thousand, two hundred forty-five".