21520325 has 6 divisors (see below), whose sum is σ = 26685234. Its totient is φ = 17216240.

The previous prime is 21520307. The next prime is 21520361. The reversal of 21520325 is 52302512.

It can be written as a sum of positive squares in 3 ways, for example, as 4 + 21520321 = 2^2 + 4639^2 .

It is not a de Polignac number, because 21520325 - 2⁸ = 21520069 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21520297 and 21520306.

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 5 ways as a sum of consecutive naturals, for example, 430382 + ... + 430431.

It is an arithmetic number, because the mean of its divisors is an integer number (4447539).

Almost surely, 2^21520325 is an apocalyptic number.

21520325 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21520325 is a deficient number, since it is larger than the sum of its proper divisors (5164909).

21520325 is an equidigital number, since it uses as much as digits as its factorization.

21520325 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 860823 (or 860818 counting only the distinct ones).

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

The square root of 21520325 is about 4639.0004311274. Note that the first 3 decimals coincide. The cubic root of 21520325 is about 278.1524835021.

Adding to 21520325 its reverse (52302512), we get a palindrome (73822837).

The spelling of 21520325 in words is "twenty-one million, five hundred twenty thousand, three hundred twenty-five".