21028217 has 8 divisors (see below), whose sum is σ = 24078912. Its totient is φ = 17989200.

The previous prime is 21028213. The next prime is 21028229. The reversal of 21028217 is 71282012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21028217 - 2² = 21028213 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21028192 and 21028201.

It is not an unprimeable number, because it can be changed into a prime (21028211) 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 7 ways as a sum of consecutive naturals, for example, 1367 + ... + 6627.

It is an arithmetic number, because the mean of its divisors is an integer number (3009864).

Almost surely, 2^21028217 is an apocalyptic number.

It is an amenable number.

21028217 is a deficient number, since it is larger than the sum of its proper divisors (3050695).

21028217 is an equidigital number, since it uses as much as digits as its factorization.

21028217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5839.

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21028217 is about 4585.6533885587. The cubic root of 21028217 is about 276.0159314825.

The spelling of 21028217 in words is "twenty-one million, twenty-eight thousand, two hundred seventeen".