2091581 has 2 divisors, whose sum is σ = 2091582. Its totient is φ = 2091580.

The previous prime is 2091553. The next prime is 2091587. The reversal of 2091581 is 1851902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1865956 + 225625 = 1366^2 + 475^2 .

It is a cyclic number.

It is not a de Polignac number, because 2091581 - 2¹⁴ = 2075197 is a prime.

It is a super-2 number, since 2×2091581² = 8749422159122, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 2091581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2091587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1045790 + 1045791.

It is an arithmetic number, because the mean of its divisors is an integer number (1045791).

2^2091581 is an apocalyptic number.

It is an amenable number.

2091581 is a deficient number, since it is larger than the sum of its proper divisors (1).

2091581 is an equidigital number, since it uses as much as digits as its factorization.

2091581 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 2091581 is about 1446.2299263948. The cubic root of 2091581 is about 127.8865572034.

The spelling of 2091581 in words is "two million, ninety-one thousand, five hundred eighty-one".