21128559 has 16 divisors (see below), whose sum is σ = 30412800. Its totient is φ = 13007456.

The previous prime is 21128543. The next prime is 21128561. The reversal of 21128559 is 95582112.

It is a cyclic number.

It is not a de Polignac number, because 21128559 - 2⁴ = 21128543 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21128539) 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 15 ways as a sum of consecutive naturals, for example, 3279 + ... + 7280.

It is an arithmetic number, because the mean of its divisors is an integer number (1900800).

Almost surely, 2^21128559 is an apocalyptic number.

21128559 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21128559 is a deficient number, since it is larger than the sum of its proper divisors (9284241).

21128559 is a wasteful number, since it uses less digits than its factorization.

21128559 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10614.

The product of its digits is 7200, while the sum is 33.

The square root of 21128559 is about 4596.5812295662. The cubic root of 21128559 is about 276.4542640012.

The spelling of 21128559 in words is "twenty-one million, one hundred twenty-eight thousand, five hundred fifty-nine".