1991781803 has 8 divisors (see below), whose sum is σ = 2174561856. Its totient is φ = 1809286600.

The previous prime is 1991781791. The next prime is 1991781833. The reversal of 1991781803 is 3081871991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1991781803 - 2¹⁶ = 1991716267 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991781833) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 56453 + ... + 84678.

It is an arithmetic number, because the mean of its divisors is an integer number (271820232).

Almost surely, 2^1991781803 is an apocalyptic number.

1991781803 is a deficient number, since it is larger than the sum of its proper divisors (182780053).

1991781803 is a wasteful number, since it uses less digits than its factorization.

1991781803 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142425.

The product of its (nonzero) digits is 108864, while the sum is 47.

The square root of 1991781803 is about 44629.3827315593. The cubic root of 1991781803 is about 1258.1929675435.

The spelling of 1991781803 in words is "one billion, nine hundred ninety-one million, seven hundred eighty-one thousand, eight hundred three".