21688304 has 20 divisors (see below), whose sum is σ = 45841560. Its totient is φ = 9858240.

The previous prime is 21688301. The next prime is 21688307. The reversal of 21688304 is 40388612.

It is an interprime number because it is at equal distance from previous prime (21688301) and next prime (21688307).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21688301) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61439 + ... + 61790.

It is an arithmetic number, because the mean of its divisors is an integer number (2292078).

Almost surely, 2^21688304 is an apocalyptic number.

It is an amenable number.

21688304 is an abundant number, since it is smaller than the sum of its proper divisors (24153256).

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

21688304 is a wasteful number, since it uses less digits than its factorization.

21688304 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123248 (or 123242 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 32.

The square root of 21688304 is about 4657.0703237121. The cubic root of 21688304 is about 278.8743240796.

The spelling of 21688304 in words is "twenty-one million, six hundred eighty-eight thousand, three hundred four".