6687978 has 16 divisors (see below), whose sum is σ = 14592096. Its totient is φ = 2026640.

The previous prime is 6687973. The next prime is 6687983. The reversal of 6687978 is 8797866.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (6687973) and next prime (6687983).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 6687978.

It is not an unprimeable number, because it can be changed into a prime (6687973) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 50601 + ... + 50732.

It is an arithmetic number, because the mean of its divisors is an integer number (912006).

Almost surely, 2^6687978 is an apocalyptic number.

6687978 is an abundant number, since it is smaller than the sum of its proper divisors (7904118).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

6687978 is a wasteful number, since it uses less digits than its factorization.

6687978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101349.

The product of its digits is 1016064, while the sum is 51.

The square root of 6687978 is about 2586.1125265541. The cubic root of 6687978 is about 188.4075397833.

It can be divided in two parts, 668 and 7978, that added together give a triangular number (8646 = T₁₃₁).

The spelling of 6687978 in words is "six million, six hundred eighty-seven thousand, nine hundred seventy-eight".