6647978 has 4 divisors (see below), whose sum is σ = 9971970. Its totient is φ = 3323988.

The previous prime is 6647959. The next prime is 6647983. The reversal of 6647978 is 8797466.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 3869089 + 2778889 = 1967^2 + 1667^2 .

It is a super-2 number, since 2×6647978² = 88391222976968, which contains 22 as substring.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 1661993 + ... + 1661996.

Almost surely, 2^6647978 is an apocalyptic number.

6647978 is a deficient number, since it is larger than the sum of its proper divisors (3323992).

6647978 is a wasteful number, since it uses less digits than its factorization.

6647978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3323991.

The product of its digits is 508032, while the sum is 47.

The square root of 6647978 is about 2578.3673128552. The cubic root of 6647978 is about 188.0311740971.

The spelling of 6647978 in words is "six million, six hundred forty-seven thousand, nine hundred seventy-eight".