999997678 has 4 divisors (see below), whose sum is σ = 1499996520. Its totient is φ = 499998838.

The previous prime is 999997673. The next prime is 999997679. The reversal of 999997678 is 876799999.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 876799999 = 127 ⋅6903937.

It is a self number, because there is not a number n which added to its sum of digits gives 999997678.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999997673) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 249999418 + ... + 249999421.

It is an arithmetic number, because the mean of its divisors is an integer number (374999130).

Almost surely, 2^999997678 is an apocalyptic number.

999997678 is a deficient number, since it is larger than the sum of its proper divisors (499998842).

999997678 is a wasteful number, since it uses less digits than its factorization.

999997678 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 499998841.

The product of its digits is 138883248, while the sum is 73.

The square root of 999997678 is about 31622.7398876188. The cubic root of 999997678 is about 999.9992259994. Note that the first 3 decimals are identical.

The spelling of 999997678 in words is "nine hundred ninety-nine million, nine hundred ninety-seven thousand, six hundred seventy-eight".