21609125 has 16 divisors (see below), whose sum is σ = 28557360. Its totient is φ = 16268800.

The previous prime is 21609109. The next prime is 21609131. The reversal of 21609125 is 52190612.

It can be written as a sum of positive squares in 8 ways, for example, as 806404 + 20802721 = 898^2 + 4561^2 .

It is not a de Polignac number, because 21609125 - 2⁴ = 21609109 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21609094 and 21609103.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2960 + ... + 7209.

It is an arithmetic number, because the mean of its divisors is an integer number (1784835).

Almost surely, 2^21609125 is an apocalyptic number.

21609125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21609125 is a deficient number, since it is larger than the sum of its proper divisors (6948235).

21609125 is a wasteful number, since it uses less digits than its factorization.

21609125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10201 (or 10191 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21609125 is about 4648.5616054862. The cubic root of 21609125 is about 278.5345416235.

Adding to 21609125 its reverse (52190612), we get a palindrome (73799737).

The spelling of 21609125 in words is "twenty-one million, six hundred nine thousand, one hundred twenty-five".