647666217 has 24 divisors (see below), whose sum is σ = 1045463328. Its totient is φ = 382948800.

The previous prime is 647666209. The next prime is 647666233. The reversal of 647666217 is 712666746.

It is a happy number.

It is not a de Polignac number, because 647666217 - 2³ = 647666209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (647666207) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 75723 + ... + 83840.

It is an arithmetic number, because the mean of its divisors is an integer number (43560972).

Almost surely, 2^647666217 is an apocalyptic number.

It is an amenable number.

647666217 is a deficient number, since it is larger than the sum of its proper divisors (397797111).

647666217 is a wasteful number, since it uses less digits than its factorization.

647666217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159621 (or 159618 counting only the distinct ones).

The product of its digits is 508032, while the sum is 45.

The square root of 647666217 is about 25449.2871609403. The cubic root of 647666217 is about 865.2011369167.

The spelling of 647666217 in words is "six hundred forty-seven million, six hundred sixty-six thousand, two hundred seventeen".