2101991 has 8 divisors (see below), whose sum is σ = 2158320. Its totient is φ = 2046528.

The previous prime is 2101961. The next prime is 2102021. The reversal of 2101991 is 1991012.

It is an interprime number because it is at equal distance from previous prime (2101961) and next prime (2102021).

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

It is a cyclic number.

It is not a de Polignac number, because 2101991 - 2¹⁴ = 2085607 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 (2101961) 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, 9065 + ... + 9293.

It is an arithmetic number, because the mean of its divisors is an integer number (269790).

2^2101991 is an apocalyptic number.

2101991 is a deficient number, since it is larger than the sum of its proper divisors (56329).

2101991 is a wasteful number, since it uses less digits than its factorization.

2101991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433.

The product of its (nonzero) digits is 162, while the sum is 23.

The square root of 2101991 is about 1449.8244721345. The cubic root of 2101991 is about 128.0983740825.

The spelling of 2101991 in words is "two million, one hundred one thousand, nine hundred ninety-one".