21206317 has 8 divisors (see below), whose sum is σ = 23172480. Its totient is φ = 19246560.

The previous prime is 21206303. The next prime is 21206323. The reversal of 21206317 is 71360212.

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 21206317 - 2⁷ = 21206189 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206347) 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, 7708 + ... + 10090.

It is an arithmetic number, because the mean of its divisors is an integer number (2896560).

Almost surely, 2^21206317 is an apocalyptic number.

It is an amenable number.

21206317 is a deficient number, since it is larger than the sum of its proper divisors (1966163).

21206317 is a wasteful number, since it uses less digits than its factorization.

21206317 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3203.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21206317 is about 4605.0317045597. The cubic root of 21206317 is about 276.7929874277.

Adding to 21206317 its reverse (71360212), we get a palindrome (92566529).

The spelling of 21206317 in words is "twenty-one million, two hundred six thousand, three hundred seventeen".