21288305 has 8 divisors (see below), whose sum is σ = 25570944. Its totient is φ = 17014000.

The previous prime is 21288259. The next prime is 21288343. The reversal of 21288305 is 50388212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21288305 - 2⁸ = 21288049 is a prime.

It is a Duffinian number.

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, 7880 + ... + 10230.

It is an arithmetic number, because the mean of its divisors is an integer number (3196368).

Almost surely, 2^21288305 is an apocalyptic number.

It is an amenable number.

21288305 is a deficient number, since it is larger than the sum of its proper divisors (4282639).

21288305 is a wasteful number, since it uses less digits than its factorization.

21288305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4167.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 21288305 is about 4613.9251185948. The cubic root of 21288305 is about 277.1492416503.

The spelling of 21288305 in words is "twenty-one million, two hundred eighty-eight thousand, three hundred five".