261691242289 has 4 divisors (see below), whose sum is σ = 270715078260. Its totient is φ = 252667406320.

The previous prime is 261691242283. The next prime is 261691242311. The reversal of 261691242289 is 982242196162.

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 113016992400 + 148674249889 = 336180^2 + 385583^2 .

It is a cyclic number.

It is not a de Polignac number, because 261691242289 - 2³⁷ = 124252288817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261691242283) 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, 4511917942 + ... + 4511917999.

It is an arithmetic number, because the mean of its divisors is an integer number (67678769565).

Almost surely, 2^261691242289 is an apocalyptic number.

261691242289 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

261691242289 is a deficient number, since it is larger than the sum of its proper divisors (9023835971).

261691242289 is an equidigital number, since it uses as much as digits as its factorization.

261691242289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9023835970.

The product of its digits is 1492992, while the sum is 52.

The spelling of 261691242289 in words is "two hundred sixty-one billion, six hundred ninety-one million, two hundred forty-two thousand, two hundred eighty-nine".