78394941991 has 4 divisors (see below), whose sum is σ = 78407856832. Its totient is φ = 78382027152.

The previous prime is 78394941967. The next prime is 78394942019. The reversal of 78394941991 is 19914949387.

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 78394941991 - 2¹⁵ = 78394909223 is a prime.

It is a super-2 number, since 2×78394941991² (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 (78394941931) 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, 6448311 + ... + 6460456.

It is an arithmetic number, because the mean of its divisors is an integer number (19601964208).

Almost surely, 2^78394941991 is an apocalyptic number.

78394941991 is a deficient number, since it is larger than the sum of its proper divisors (12914841).

78394941991 is a wasteful number, since it uses less digits than its factorization.

78394941991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12914840.

The product of its digits is 17635968, while the sum is 64.

The spelling of 78394941991 in words is "seventy-eight billion, three hundred ninety-four million, nine hundred forty-one thousand, nine hundred ninety-one".