21428384 has 12 divisors (see below), whose sum is σ = 42187194. Its totient is φ = 10714176.

The previous prime is 21428383. The next prime is 21428389. The reversal of 21428384 is 48382412.

It can be written as a sum of positive squares in only one way, i.e., 21418384 + 10000 = 4628^2 + 100^2 .

It is a Harshad number since it is a multiple of its sum of digits (32), and also a Moran number because the ratio is a prime number: 669637 = 21428384 / (2 + 1 + 4 + 2 + 8 + 3 + 8 + 4).

It is a self number, because there is not a number n which added to its sum of digits gives 21428384.

It is not an unprimeable number, because it can be changed into a prime (21428383) 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 as a sum of consecutive naturals, namely, 334787 + ... + 334850.

Almost surely, 2^21428384 is an apocalyptic number.

It is an amenable number.

21428384 is a deficient number, since it is larger than the sum of its proper divisors (20758810).

21428384 is an equidigital number, since it uses as much as digits as its factorization.

21428384 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 669647 (or 669639 counting only the distinct ones).

The product of its digits is 12288, while the sum is 32.

The square root of 21428384 is about 4629.0802542190. The cubic root of 21428384 is about 277.7558023267.

It can be divided in two parts, 21428 and 384, that added together give a palindrome (21812).

The spelling of 21428384 in words is "twenty-one million, four hundred twenty-eight thousand, three hundred eighty-four".