21684648 has 16 divisors (see below), whose sum is σ = 54211680. Its totient is φ = 7228208.

The previous prime is 21684647. The next prime is 21684659. The reversal of 21684648 is 84648612.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21684647) 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 3 ways as a sum of consecutive naturals, for example, 451740 + ... + 451787.

It is an arithmetic number, because the mean of its divisors is an integer number (3388230).

Almost surely, 2^21684648 is an apocalyptic number.

It is an amenable number.

21684648 is an abundant number, since it is smaller than the sum of its proper divisors (32527032).

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

21684648 is a wasteful number, since it uses less digits than its factorization.

21684648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 903536 (or 903532 counting only the distinct ones).

The product of its digits is 73728, while the sum is 39.

The square root of 21684648 is about 4656.6777857181. The cubic root of 21684648 is about 278.8586532396.

The spelling of 21684648 in words is "twenty-one million, six hundred eighty-four thousand, six hundred forty-eight".