21417217 has 4 divisors (see below), whose sum is σ = 21442516. Its totient is φ = 21391920.

The previous prime is 21417203. The next prime is 21417233. The reversal of 21417217 is 71271412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 6548481 + 14868736 = 2559^2 + 3856^2 .

It is a cyclic number.

It is not a de Polignac number, because 21417217 - 2⁷ = 21417089 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21417191 and 21417200.

It is not an unprimeable number, because it can be changed into a prime (21417257) 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, 11334 + ... + 13087.

It is an arithmetic number, because the mean of its divisors is an integer number (5360629).

Almost surely, 2^21417217 is an apocalyptic number.

It is an amenable number.

21417217 is a deficient number, since it is larger than the sum of its proper divisors (25299).

21417217 is an equidigital number, since it uses as much as digits as its factorization.

21417217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25298.

The product of its digits is 784, while the sum is 25.

The square root of 21417217 is about 4627.8739179023. The cubic root of 21417217 is about 277.7075448691.

Adding to 21417217 its reverse (71271412), we get a palindrome (92688629).

The spelling of 21417217 in words is "twenty-one million, four hundred seventeen thousand, two hundred seventeen".