21287384 has 16 divisors (see below), whose sum is σ = 40461720. Its totient is φ = 10497600.

The previous prime is 21287347. The next prime is 21287389. The reversal of 21287384 is 48378212.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21287389) 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 3 ways as a sum of consecutive naturals, for example, 17642 + ... + 18809.

Almost surely, 2^21287384 is an apocalyptic number.

It is an amenable number.

21287384 is a deficient number, since it is larger than the sum of its proper divisors (19174336).

21287384 is a wasteful number, since it uses less digits than its factorization.

21287384 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36530 (or 36526 counting only the distinct ones).

The product of its digits is 21504, while the sum is 35.

The square root of 21287384 is about 4613.8253109540. The cubic root of 21287384 is about 277.1452448058.

The spelling of 21287384 in words is "twenty-one million, two hundred eighty-seven thousand, three hundred eighty-four".