21308025 has 36 divisors (see below), whose sum is σ = 37228272. Its totient is φ = 10752480.

The previous prime is 21308017. The next prime is 21308029. The reversal of 21308025 is 52080312.

It is not a de Polignac number, because 21308025 - 2³ = 21308017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21307992 and 21308010.

It is not an unprimeable number, because it can be changed into a prime (21308029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 26682 + ... + 27468.

Almost surely, 2^21308025 is an apocalyptic number.

21308025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21308025 is a deficient number, since it is larger than the sum of its proper divisors (15920247).

21308025 is a wasteful number, since it uses less digits than its factorization.

21308025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 838 (or 814 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21308025 is about 4616.0616330374. The cubic root of 21308025 is about 277.2347924778.

Adding to 21308025 its reverse (52080312), we get a palindrome (73388337).

The spelling of 21308025 in words is "twenty-one million, three hundred eight thousand, twenty-five".