21485 has 4 divisors (see below), whose sum is σ = 25788. Its totient is φ = 17184.

The previous prime is 21481. The next prime is 21487. The reversal of 21485 is 58412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9604 + 11881 = 98^2 + 109^2 .

It is a cyclic number.

It is not a de Polignac number, because 21485 - 2² = 21481 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2144 + ... + 2153.

It is an arithmetic number, because the mean of its divisors is an integer number (6447).

2²¹⁴⁸⁵ is an apocalyptic number.

It is an amenable number.

21485 is a deficient number, since it is larger than the sum of its proper divisors (4303).

21485 is an equidigital number, since it uses as much as digits as its factorization.

21485 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4302.

The product of its digits is 320, while the sum is 20.

The square root of 21485 is about 146.5776244861. The cubic root of 21485 is about 27.8000207028.

Adding to 21485 its reverse (58412), we get a palindrome (79897).

The spelling of 21485 in words is "twenty-one thousand, four hundred eighty-five".