21220528 has 30 divisors (see below), whose sum is σ = 47829156. Its totient is φ = 9094176.

The previous prime is 21220501. The next prime is 21220531. The reversal of 21220528 is 82502212.

It is a junction number, because it is equal to n+sod(n) for n = 21220499 and 21220508.

It is an unprimeable number.

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 in 5 ways as a sum of consecutive naturals, for example, 12750 + ... + 14317.

Almost surely, 2^21220528 is an apocalyptic number.

21220528 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21220528 is an abundant number, since it is smaller than the sum of its proper divisors (26608628).

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

21220528 is a wasteful number, since it uses less digits than its factorization.

21220528 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27089 (or 27076 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 22.

The square root of 21220528 is about 4606.5744322653. The cubic root of 21220528 is about 276.8548027635.

The spelling of 21220528 in words is "twenty-one million, two hundred twenty thousand, five hundred twenty-eight".