21428128 has 24 divisors (see below), whose sum is σ = 42769188. Its totient is φ = 10566144.

The previous prime is 21428123. The next prime is 21428131. The reversal of 21428128 is 82182412.

It can be written as a sum of positive squares in 2 ways, for example, as 19820304 + 1607824 = 4452^2 + 1268^2 .

It is a nude number because it is divisible by every one of its digits.

It is a junction number, because it is equal to n+sod(n) for n = 21428096 and 21428105.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21428123) 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 3 ways as a sum of consecutive naturals, for example, 2251 + ... + 6922.

Almost surely, 2^21428128 is an apocalyptic number.

It is an amenable number.

21428128 is a deficient number, since it is larger than the sum of its proper divisors (21341060).

21428128 is an equidigital number, since it uses as much as digits as its factorization.

21428128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9256 (or 9248 counting only the distinct ones).

The product of its digits is 2048, while the sum is 28.

The square root of 21428128 is about 4629.0526028551. The cubic root of 21428128 is about 277.7546962273.

The spelling of 21428128 in words is "twenty-one million, four hundred twenty-eight thousand, one hundred twenty-eight".