21906648 has 24 divisors (see below), whose sum is σ = 59330700. Its totient is φ = 7302192.

The previous prime is 21906631. The next prime is 21906667. The reversal of 21906648 is 84660912.

21906648 is a `hidden beast` number, since 2 + 1 + 9 + 0 + 6 + 648 = 666.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

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 5 ways as a sum of consecutive naturals, for example, 152058 + ... + 152201.

Almost surely, 2^21906648 is an apocalyptic number.

It is an amenable number.

21906648 is an abundant number, since it is smaller than the sum of its proper divisors (37424052).

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

21906648 is a wasteful number, since it uses less digits than its factorization.

21906648 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304271 (or 304264 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 21906648 is about 4680.4538241500. The cubic root of 21906648 is about 279.8070439297.

The spelling of 21906648 in words is "twenty-one million, nine hundred six thousand, six hundred forty-eight".