21028755 has 16 divisors (see below), whose sum is σ = 36705024. Its totient is φ = 10195680.

The previous prime is 21028747. The next prime is 21028759. The reversal of 21028755 is 55782012.

It is not a de Polignac number, because 21028755 - 2³ = 21028747 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21028759) 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, 63559 + ... + 63888.

It is an arithmetic number, because the mean of its divisors is an integer number (2294064).

Almost surely, 2^21028755 is an apocalyptic number.

21028755 is a deficient number, since it is larger than the sum of its proper divisors (15676269).

21028755 is a wasteful number, since it uses less digits than its factorization.

21028755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127466.

The product of its (nonzero) digits is 5600, while the sum is 30.

The square root of 21028755 is about 4585.7120493987. The cubic root of 21028755 is about 276.0182853880.

The spelling of 21028755 in words is "twenty-one million, twenty-eight thousand, seven hundred fifty-five".