21288818 has 4 divisors (see below), whose sum is σ = 31933230. Its totient is φ = 10644408.

The previous prime is 21288779. The next prime is 21288829. The reversal of 21288818 is 81888212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20948929 + 339889 = 4577^2 + 583^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5322203 + ... + 5322206.

Almost surely, 2^21288818 is an apocalyptic number.

21288818 is a deficient number, since it is larger than the sum of its proper divisors (10644412).

21288818 is a wasteful number, since it uses less digits than its factorization.

21288818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10644411.

The product of its digits is 16384, while the sum is 38.

The square root of 21288818 is about 4613.9807108396. The cubic root of 21288818 is about 277.1514678557.

The spelling of 21288818 in words is "twenty-one million, two hundred eighty-eight thousand, eight hundred eighteen".