21309425 has 12 divisors (see below), whose sum is σ = 26486400. Its totient is φ = 17007120.

The previous prime is 21309401. The next prime is 21309433. The reversal of 21309425 is 52490312.

It is not a de Polignac number, because 21309425 - 2¹⁸ = 21047281 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21309394 and 21309403.

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 11 ways as a sum of consecutive naturals, for example, 14264 + ... + 15686.

It is an arithmetic number, because the mean of its divisors is an integer number (2207200).

Almost surely, 2^21309425 is an apocalyptic number.

21309425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21309425 is a deficient number, since it is larger than the sum of its proper divisors (5176975).

21309425 is a wasteful number, since it uses less digits than its factorization.

21309425 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2032 (or 2027 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 26.

The square root of 21309425 is about 4616.2132749690. The cubic root of 21309425 is about 277.2408640590.

Adding to 21309425 its reverse (52490312), we get a palindrome (73799737).

The spelling of 21309425 in words is "twenty-one million, three hundred nine thousand, four hundred twenty-five".