2091781 has 4 divisors (see below), whose sum is σ = 2182752. Its totient is φ = 2000812.

The previous prime is 2091773. The next prime is 2091797. The reversal of 2091781 is 1871902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2091781 - 2³ = 2091773 is a prime.

It is a super-2 number, since 2×2091781² = 8751095503922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2091281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45451 + ... + 45496.

It is an arithmetic number, because the mean of its divisors is an integer number (545688).

2^2091781 is an apocalyptic number.

It is an amenable number.

2091781 is a deficient number, since it is larger than the sum of its proper divisors (90971).

2091781 is an equidigital number, since it uses as much as digits as its factorization.

2091781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90970.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 2091781 is about 1446.2990700405. The cubic root of 2091781 is about 127.8906333060.

The spelling of 2091781 in words is "two million, ninety-one thousand, seven hundred eighty-one".