21305648 has 40 divisors (see below), whose sum is σ = 50809248. Its totient is φ = 8428032.

The previous prime is 21305639. The next prime is 21305651. The reversal of 21305648 is 84650312.

It is a self number, because there is not a number n which added to its sum of digits gives 21305648.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5861 + ... + 8772.

Almost surely, 2^21305648 is an apocalyptic number.

21305648 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21305648 is an abundant number, since it is smaller than the sum of its proper divisors (29503600).

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

21305648 is a wasteful number, since it uses less digits than its factorization.

21305648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14661 (or 14655 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21305648 is about 4615.8041552908. The cubic root of 21305648 is about 277.2244831913.

The spelling of 21305648 in words is "twenty-one million, three hundred five thousand, six hundred forty-eight".