2100009991 has 4 divisors (see below), whose sum is σ = 2100103632. Its totient is φ = 2099916352.

The previous prime is 2100009943. The next prime is 2100010021. The reversal of 2100009991 is 1999000012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 2100009991 - 2²⁹ = 1563139079 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2100009931) 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, 9015 + ... + 65431.

It is an arithmetic number, because the mean of its divisors is an integer number (525025908).

Almost surely, 2^2100009991 is an apocalyptic number.

2100009991 is a deficient number, since it is larger than the sum of its proper divisors (93641).

2100009991 is an equidigital number, since it uses as much as digits as its factorization.

2100009991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93640.

The product of its (nonzero) digits is 1458, while the sum is 31.

The square root of 2100009991 is about 45825.8659601758. The cubic root of 2100009991 is about 1280.5811958202.

The spelling of 2100009991 in words is "two billion, one hundred million, nine thousand, nine hundred ninety-one".