2191081 has 4 divisors (see below), whose sum is σ = 2244564. Its totient is φ = 2137600.

The previous prime is 2191069. The next prime is 2191087. The reversal of 2191081 is 1801912.

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 665856 + 1525225 = 816^2 + 1235^2 .

It is a cyclic number.

It is not a de Polignac number, because 2191081 - 2¹⁹ = 1666793 is a prime.

It is a super-2 number, since 2×2191081² = 9601671897122, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

2191081 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (2191087) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26680 + ... + 26761.

It is an arithmetic number, because the mean of its divisors is an integer number (561141).

2^2191081 is an apocalyptic number.

It is an amenable number.

2191081 is a deficient number, since it is larger than the sum of its proper divisors (53483).

2191081 is an equidigital number, since it uses as much as digits as its factorization.

2191081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53482.

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 2191081 is about 1480.2300496882. The cubic root of 2191081 is about 129.8831494382.

Adding to 2191081 its reverse (1801912), we get a palindrome (3992993).

The spelling of 2191081 in words is "two million, one hundred ninety-one thousand, eighty-one".