1091561 has 2 divisors, whose sum is σ = 1091562. Its totient is φ = 1091560.

The previous prime is 1091551. The next prime is 1091581. The reversal of 1091561 is 1651901.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 755161 + 336400 = 869^2 + 580^2 .

It is a cyclic number.

It is not a de Polignac number, because 1091561 - 2¹⁴ = 1075177 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1091521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 545780 + 545781.

It is an arithmetic number, because the mean of its divisors is an integer number (545781).

2^1091561 is an apocalyptic number.

It is an amenable number.

1091561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1091561 is an equidigital number, since it uses as much as digits as its factorization.

1091561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 270, while the sum is 23.

The square root of 1091561 is about 1044.7779668427. Note that the first 3 decimals coincide. The cubic root of 1091561 is about 102.9633514005.

The spelling of 1091561 in words is "one million, ninety-one thousand, five hundred sixty-one".