646665566647 has 8 divisors (see below), whose sum is σ = 680302760400. Its totient is φ = 613784265024.

The previous prime is 646665566633. The next prime is 646665566681. The reversal of 646665566647 is 746665566646.

It is a happy number.

646665566647 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 646665566647 - 2¹⁵ = 646665533879 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 (646665563647) 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, 188971278 + ... + 188974699.

It is an arithmetic number, because the mean of its divisors is an integer number (85037845050).

Almost surely, 2^646665566647 is an apocalyptic number.

646665566647 is a deficient number, since it is larger than the sum of its proper divisors (33637193753).

646665566647 is a wasteful number, since it uses less digits than its factorization.

646665566647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 377946065.

The product of its digits is 783820800, while the sum is 67.

Subtracting 646665566647 from its reverse (746665566646), we obtain a palindrome (99999999999).

The spelling of 646665566647 in words is "six hundred forty-six billion, six hundred sixty-five million, five hundred sixty-six thousand, six hundred forty-seven".