21225 has 12 divisors (see below), whose sum is σ = 35216. Its totient is φ = 11280.

The previous prime is 21221. The next prime is 21227. The reversal of 21225 is 52212.

It is not a de Polignac number, because 21225 - 2² = 21221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21225.

It is not an unprimeable number, because it can be changed into a prime (21221) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 67 + ... + 216.

2²¹²²⁵ is an apocalyptic number.

21225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21225 is a deficient number, since it is larger than the sum of its proper divisors (13991).

21225 is a wasteful number, since it uses less digits than its factorization.

21225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 296 (or 291 counting only the distinct ones).

The product of its digits is 40, while the sum is 12.

The square root of 21225 is about 145.6880228433. The cubic root of 21225 is about 27.6874249463.

Adding to 21225 its reverse (52212), we get a palindrome (73437).

The spelling of 21225 in words is "twenty-one thousand, two hundred twenty-five".