1991788 has 18 divisors (see below), whose sum is σ = 3704876. Its totient is φ = 936768.

The previous prime is 1991779. The next prime is 1991797. The reversal of 1991788 is 8871991.

It is an interprime number because it is at equal distance from previous prime (1991779) and next prime (1991797).

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 in 5 ways as a sum of consecutive naturals, for example, 295 + ... + 2017.

2^1991788 is an apocalyptic number.

It is an amenable number.

1991788 is a deficient number, since it is larger than the sum of its proper divisors (1713088).

1991788 is a wasteful number, since it uses less digits than its factorization.

1991788 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1761 (or 1742 counting only the distinct ones).

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

The square root of 1991788 is about 1411.3071954752. The cubic root of 1991788 is about 125.8194272408.

The spelling of 1991788 in words is "one million, nine hundred ninety-one thousand, seven hundred eighty-eight".