21530225 has 12 divisors (see below), whose sum is σ = 26945820. Its totient is φ = 17064000.

The previous prime is 21530161. The next prime is 21530227. The reversal of 21530225 is 52203512.

It can be written as a sum of positive squares in 6 ways, for example, as 65536 + 21464689 = 256^2 + 4633^2 .

It is not a de Polignac number, because 21530225 - 2⁶ = 21530161 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21530197 and 21530206.

It is not an unprimeable number, because it can be changed into a prime (21530227) 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, 1226 + ... + 6675.

It is an arithmetic number, because the mean of its divisors is an integer number (2245485).

Almost surely, 2^21530225 is an apocalyptic number.

21530225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21530225 is a deficient number, since it is larger than the sum of its proper divisors (5415595).

21530225 is a wasteful number, since it uses less digits than its factorization.

21530225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8020 (or 8015 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 20.

The square root of 21530225 is about 4640.0673486492. The cubic root of 21530225 is about 278.1951298133.

Adding to 21530225 its reverse (52203512), we get a palindrome (73733737).

The spelling of 21530225 in words is "twenty-one million, five hundred thirty thousand, two hundred twenty-five".