391997678 has 8 divisors (see below), whose sum is σ = 593200368. Its totient is φ = 194264224.

The previous prime is 391997677. The next prime is 391997701. The reversal of 391997678 is 876799193.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (391997677) 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, 867026 + ... + 867477.

It is an arithmetic number, because the mean of its divisors is an integer number (74150046).

Almost surely, 2^391997678 is an apocalyptic number.

391997678 is a deficient number, since it is larger than the sum of its proper divisors (201202690).

391997678 is a wasteful number, since it uses less digits than its factorization.

391997678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1734618.

The product of its digits is 5143824, while the sum is 59.

The square root of 391997678 is about 19798.9312337813. The cubic root of 391997678 is about 731.8596969494.

The spelling of 391997678 in words is "three hundred ninety-one million, nine hundred ninety-seven thousand, six hundred seventy-eight".