21305025 has 84 divisors (see below), whose sum is σ = 45538752. Its totient is φ = 9681120.

The previous prime is 21305003. The next prime is 21305027. The reversal of 21305025 is 52050312.

It is a happy number.

It is not a de Polignac number, because 21305025 - 2⁷ = 21304897 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21304989 and 21305007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21305027) by changing a digit.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 127492 + ... + 127658.

It is an arithmetic number, because the mean of its divisors is an integer number (542128).

Almost surely, 2^21305025 is an apocalyptic number.

21305025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21305025 is an abundant number, since it is smaller than the sum of its proper divisors (24233727).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21305025 is an equidigital number, since it uses as much as digits as its factorization.

21305025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202 (or 182 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 18.

The square root of 21305025 is about 4615.7366692653. The cubic root of 21305025 is about 277.2217810512.

Adding to 21305025 its reverse (52050312), we get a palindrome (73355337).

The spelling of 21305025 in words is "twenty-one million, three hundred five thousand, twenty-five".