21020217 has 8 divisors (see below), whose sum is σ = 28089600. Its totient is φ = 13982160.

The previous prime is 21020161. The next prime is 21020227. The reversal of 21020217 is 71202012.

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

It is not a de Polignac number, because 21020217 - 2⁷ = 21020089 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21020196 and 21020205.

It is not an unprimeable number, because it can be changed into a prime (21020227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6217 + ... + 8982.

It is an arithmetic number, because the mean of its divisors is an integer number (3511200).

Almost surely, 2^21020217 is an apocalyptic number.

It is an amenable number.

21020217 is a deficient number, since it is larger than the sum of its proper divisors (7069383).

21020217 is a wasteful number, since it uses less digits than its factorization.

21020217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15663.

The product of its (nonzero) digits is 56, while the sum is 15.

The square root of 21020217 is about 4584.7810198525. The cubic root of 21020217 is about 275.9809244325.

Adding to 21020217 its reverse (71202012), we get a palindrome (92222229).

The spelling of 21020217 in words is "twenty-one million, twenty thousand, two hundred seventeen".