261091109 has 2 divisors, whose sum is σ = 261091110. Its totient is φ = 261091108.

The previous prime is 261091097. The next prime is 261091139. The reversal of 261091109 is 901190162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 153388225 + 107702884 = 12385^2 + 10378^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261091109 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261091139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130545554 + 130545555.

It is an arithmetic number, because the mean of its divisors is an integer number (130545555).

Almost surely, 2^261091109 is an apocalyptic number.

It is an amenable number.

261091109 is a deficient number, since it is larger than the sum of its proper divisors (1).

261091109 is an equidigital number, since it uses as much as digits as its factorization.

261091109 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 972, while the sum is 29.

The square root of 261091109 is about 16158.3139281300. The cubic root of 261091109 is about 639.1420053829.

The spelling of 261091109 in words is "two hundred sixty-one million, ninety-one thousand, one hundred nine".