6921978 has 16 divisors (see below), whose sum is σ = 15821760. Its totient is φ = 1977696.

The previous prime is 6921961. The next prime is 6922001. The reversal of 6921978 is 8791296.

It is a Harshad number since it is a multiple of its sum of digits (42), and also a Moran number because the ratio is a prime number: 164809 = 6921978 / (6 + 9 + 2 + 1 + 9 + 7 + 8).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 82363 + ... + 82446.

It is an arithmetic number, because the mean of its divisors is an integer number (988860).

Almost surely, 2^6921978 is an apocalyptic number.

6921978 is an abundant number, since it is smaller than the sum of its proper divisors (8899782).

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

6921978 is a wasteful number, since it uses less digits than its factorization.

6921978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164821.

The product of its digits is 54432, while the sum is 42.

The square root of 6921978 is about 2630.9652221191. The cubic root of 6921978 is about 190.5797435519.

The spelling of 6921978 in words is "six million, nine hundred twenty-one thousand, nine hundred seventy-eight".