1991878 has 16 divisors (see below), whose sum is σ = 3463200. Its totient is φ = 841536.

The previous prime is 1991863. The next prime is 1991879. The reversal of 1991878 is 8781991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991879) 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, 48 + ... + 1996.

It is an arithmetic number, because the mean of its divisors is an integer number (216450).

2^1991878 is an apocalyptic number.

1991878 is a deficient number, since it is larger than the sum of its proper divisors (1471322).

1991878 is a wasteful number, since it uses less digits than its factorization.

1991878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2031.

The product of its digits is 36288, while the sum is 43.

The square root of 1991878 is about 1411.3390804481. The cubic root of 1991878 is about 125.8213222848.

The spelling of 1991878 in words is "one million, nine hundred ninety-one thousand, eight hundred seventy-eight".