21288975 has 24 divisors (see below), whose sum is σ = 35338512. Its totient is φ = 11308800.

The previous prime is 21288973. The next prime is 21288983. The reversal of 21288975 is 57988212.

It is not a de Polignac number, because 21288975 - 2¹ = 21288973 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21288973) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 27595 + ... + 28355.

It is an arithmetic number, because the mean of its divisors is an integer number (1472438).

Almost surely, 2^21288975 is an apocalyptic number.

21288975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21288975 is a deficient number, since it is larger than the sum of its proper divisors (14049537).

21288975 is a wasteful number, since it uses less digits than its factorization.

21288975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1147 (or 1142 counting only the distinct ones).

The product of its digits is 80640, while the sum is 42.

The square root of 21288975 is about 4613.9977243167. The cubic root of 21288975 is about 277.1521491629.

The spelling of 21288975 in words is "twenty-one million, two hundred eighty-eight thousand, nine hundred seventy-five".