1991943801 has 12 divisors (see below), whose sum is σ = 2938470912. Its totient is φ = 1299707736.

The previous prime is 1991943787. The next prime is 1991943817. The reversal of 1991943801 is 1083491991.

It is not a de Polignac number, because 1991943801 - 2⁷ = 1991943673 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1991943901) by changing a digit.

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 in 11 ways as a sum of consecutive naturals, for example, 2354121 + ... + 2354966.

It is an arithmetic number, because the mean of its divisors is an integer number (244872576).

Almost surely, 2^1991943801 is an apocalyptic number.

It is an amenable number.

1991943801 is a deficient number, since it is larger than the sum of its proper divisors (946527111).

1991943801 is a wasteful number, since it uses less digits than its factorization.

1991943801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4709140 (or 4709137 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 45.

The square root of 1991943801 is about 44631.1976200505. The cubic root of 1991943801 is about 1258.2270775747.

The spelling of 1991943801 in words is "one billion, nine hundred ninety-one million, nine hundred forty-three thousand, eight hundred one".