20647217 has 4 divisors (see below), whose sum is σ = 21359220. Its totient is φ = 19935216.

The previous prime is 20647201. The next prime is 20647229. The reversal of 20647217 is 71274602.

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 13512976 + 7134241 = 3676^2 + 2671^2 .

It is a cyclic number.

It is not a de Polignac number, because 20647217 - 2⁴ = 20647201 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 711973 = 20647217 / (2 + 0 + 6 + 4 + 7 + 2 + 1 + 7).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20647217.

It is not an unprimeable number, because it can be changed into a prime (20647117) 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, 355958 + ... + 356015.

It is an arithmetic number, because the mean of its divisors is an integer number (5339805).

Almost surely, 2^20647217 is an apocalyptic number.

It is an amenable number.

20647217 is a deficient number, since it is larger than the sum of its proper divisors (712003).

20647217 is an equidigital number, since it uses as much as digits as its factorization.

20647217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 712002.

The product of its (nonzero) digits is 4704, while the sum is 29.

The square root of 20647217 is about 4543.9208839944. The cubic root of 20647217 is about 274.3387617383.

The spelling of 20647217 in words is "twenty million, six hundred forty-seven thousand, two hundred seventeen".