21906304 has 64 divisors (see below), whose sum is σ = 52093440. Its totient is φ = 8971776.

The previous prime is 21906301. The next prime is 21906317. The reversal of 21906304 is 40360912.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906301) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20077 + ... + 21139.

It is an arithmetic number, because the mean of its divisors is an integer number (813960).

Almost surely, 2^21906304 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21906304, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26046720).

21906304 is an abundant number, since it is smaller than the sum of its proper divisors (30187136).

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

21906304 is a wasteful number, since it uses less digits than its factorization.

21906304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1107 (or 1095 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 21906304 is about 4680.4170754325. The cubic root of 21906304 is about 279.8055793191.

The spelling of 21906304 in words is "twenty-one million, nine hundred six thousand, three hundred four".