261735991 has 8 divisors (see below), whose sum is σ = 295376400. Its totient is φ = 229736640.

The previous prime is 261735989. The next prime is 261736009. The reversal of 261735991 is 199537162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261735991 - 2¹ = 261735989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261735931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 409926 + ... + 410563.

It is an arithmetic number, because the mean of its divisors is an integer number (36922050).

Almost surely, 2^261735991 is an apocalyptic number.

261735991 is a deficient number, since it is larger than the sum of its proper divisors (33640409).

261735991 is a wasteful number, since it uses less digits than its factorization.

261735991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 820529.

The product of its digits is 102060, while the sum is 43.

The square root of 261735991 is about 16178.2567355077. The cubic root of 261735991 is about 639.6677890116.

The spelling of 261735991 in words is "two hundred sixty-one million, seven hundred thirty-five thousand, nine hundred ninety-one".