78217641647 has 4 divisors (see below), whose sum is σ = 78909833280. Its totient is φ = 77525450016.

The previous prime is 78217641643. The next prime is 78217641659. The reversal of 78217641647 is 74614671287.

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

It is a cyclic number.

It is not a de Polignac number, because 78217641647 - 2² = 78217641643 is a prime.

It is a super-2 number, since 2×78217641647² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78217641643) 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, 346095647 + ... + 346095872.

It is an arithmetic number, because the mean of its divisors is an integer number (19727458320).

Almost surely, 2^78217641647 is an apocalyptic number.

78217641647 is a deficient number, since it is larger than the sum of its proper divisors (692191633).

78217641647 is a wasteful number, since it uses less digits than its factorization.

78217641647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 692191632.

The product of its digits is 3161088, while the sum is 53.

The spelling of 78217641647 in words is "seventy-eight billion, two hundred seventeen million, six hundred forty-one thousand, six hundred forty-seven".