2991978 has 80 divisors (see below), whose sum is σ = 7736256. Its totient is φ = 855360.

The previous prime is 2991971. The next prime is 2992007. The reversal of 2991978 is 8791992.

Its product of digits (81648) is a multiple of the sum of its prime divisors (112).

It is not an unprimeable number, because it can be changed into a prime (2991971) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 40950 + ... + 41022.

2^2991978 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 2991978, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3868128).

2991978 is an abundant number, since it is smaller than the sum of its proper divisors (4744278).

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

2991978 is a wasteful number, since it uses less digits than its factorization.

2991978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121 (or 112 counting only the distinct ones).

The product of its digits is 81648, while the sum is 45.

The square root of 2991978 is about 1729.7335054857. The cubic root of 2991978 is about 144.0962897654.

It can be divided in two parts, 2991 and 978, that added together give a square (3969 = 63²).

The spelling of 2991978 in words is "two million, nine hundred ninety-one thousand, nine hundred seventy-eight".