21288965 has 8 divisors (see below), whose sum is σ = 25577208. Its totient is φ = 17010880.

The previous prime is 21288959. The next prime is 21288973. The reversal of 21288965 is 56988212.

It can be written as a sum of positive squares in 4 ways, for example, as 6558721 + 14730244 = 2561^2 + 3838^2 .

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

It is not a de Polignac number, because 21288965 - 2⁶ = 21288901 is a prime.

It is a Duffinian number.

It is a congruent 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, 3299 + ... + 7311.

It is an arithmetic number, because the mean of its divisors is an integer number (3197151).

Almost surely, 2^21288965 is an apocalyptic number.

It is an amenable number.

21288965 is a deficient number, since it is larger than the sum of its proper divisors (4288243).

21288965 is a wasteful number, since it uses less digits than its factorization.

21288965 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5079.

The product of its digits is 69120, while the sum is 41.

The square root of 21288965 is about 4613.9966406576. The cubic root of 21288965 is about 277.1521057676.

The spelling of 21288965 in words is "twenty-one million, two hundred eighty-eight thousand, nine hundred sixty-five".