1991010001 has 4 divisors (see below), whose sum is σ = 1992887604. Its totient is φ = 1989132400.

The previous prime is 1991009987. The next prime is 1991010013. The reversal of 1991010001 is 1000101991.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 572357776 + 1418652225 = 23924^2 + 37665^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991010001 - 2⁷ = 1991009873 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991010041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 937210 + ... + 939331.

It is an arithmetic number, because the mean of its divisors is an integer number (498221901).

Almost surely, 2^1991010001 is an apocalyptic number.

It is an amenable number.

1991010001 is a deficient number, since it is larger than the sum of its proper divisors (1877603).

1991010001 is a wasteful number, since it uses less digits than its factorization.

1991010001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1877602.

The product of its (nonzero) digits is 81, while the sum is 22.

The square root of 1991010001 is about 44620.7351015198. The cubic root of 1991010001 is about 1258.0304327881.

Adding to 1991010001 its reverse (1000101991), we get a palindrome (2991111992).

The spelling of 1991010001 in words is "one billion, nine hundred ninety-one million, ten thousand, one".