21028776 has 16 divisors (see below), whose sum is σ = 52572000. Its totient is φ = 7009584.

The previous prime is 21028771. The next prime is 21028823. The reversal of 21028776 is 67782012.

It is not an unprimeable number, because it can be changed into a prime (21028771) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 438076 + ... + 438123.

It is an arithmetic number, because the mean of its divisors is an integer number (3285750).

Almost surely, 2^21028776 is an apocalyptic number.

It is an amenable number.

21028776 is an abundant number, since it is smaller than the sum of its proper divisors (31543224).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21028776 is a wasteful number, since it uses less digits than its factorization.

21028776 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 876208 (or 876204 counting only the distinct ones).

The product of its (nonzero) digits is 9408, while the sum is 33.

The square root of 21028776 is about 4585.7143391188. The cubic root of 21028776 is about 276.0183772682.

It can be divided in two parts, 2102 and 8776, that added together give a triangular number (10878 = T₁₄₇).

The spelling of 21028776 in words is "twenty-one million, twenty-eight thousand, seven hundred seventy-six".