1990878686 has 4 divisors (see below), whose sum is σ = 2986318032. Its totient is φ = 995439342.

The previous prime is 1990878679. The next prime is 1990878707. The reversal of 1990878686 is 6868780991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 6868780991 = 19 ⋅361514789.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 497719670 + ... + 497719673.

It is an arithmetic number, because the mean of its divisors is an integer number (746579508).

Almost surely, 2^1990878686 is an apocalyptic number.

1990878686 is a deficient number, since it is larger than the sum of its proper divisors (995439346).

1990878686 is an equidigital number, since it uses as much as digits as its factorization.

1990878686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 995439345.

The product of its (nonzero) digits is 10450944, while the sum is 62.

The square root of 1990878686 is about 44619.2636201002. The cubic root of 1990878686 is about 1258.0027748158.

The spelling of 1990878686 in words is "one billion, nine hundred ninety million, eight hundred seventy-eight thousand, six hundred eighty-six".