21288817 has 8 divisors (see below), whose sum is σ = 23605632. Its totient is φ = 19035600.

The previous prime is 21288779. The next prime is 21288829. The reversal of 21288817 is 71888212.

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

It is a cyclic number.

It is not a de Polignac number, because 21288817 - 2¹⁹ = 20764529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21288857) by changing a digit.

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 in 7 ways as a sum of consecutive naturals, for example, 15193 + ... + 16534.

It is an arithmetic number, because the mean of its divisors is an integer number (2950704).

Almost surely, 2^21288817 is an apocalyptic number.

It is an amenable number.

21288817 is a deficient number, since it is larger than the sum of its proper divisors (2316815).

21288817 is a wasteful number, since it uses less digits than its factorization.

21288817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31799.

The product of its digits is 14336, while the sum is 37.

The square root of 21288817 is about 4613.9806024733. The cubic root of 21288817 is about 277.1514635161.

The spelling of 21288817 in words is "twenty-one million, two hundred eighty-eight thousand, eight hundred seventeen".