261686721 has 8 divisors (see below), whose sum is σ = 349156224. Its totient is φ = 174337520.

The previous prime is 261686713. The next prime is 261686731. The reversal of 261686721 is 127686162.

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 261686721 - 2³ = 261686713 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 261686721.

It is not an unprimeable number, because it can be changed into a prime (261686731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24870 + ... + 33791.

It is an arithmetic number, because the mean of its divisors is an integer number (43644528).

Almost surely, 2^261686721 is an apocalyptic number.

It is an amenable number.

261686721 is a deficient number, since it is larger than the sum of its proper divisors (87469503).

261686721 is a wasteful number, since it uses less digits than its factorization.

261686721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60151.

The product of its digits is 48384, while the sum is 39.

The square root of 261686721 is about 16176.7339410649. The cubic root of 261686721 is about 639.6276488057.

The spelling of 261686721 in words is "two hundred sixty-one million, six hundred eighty-six thousand, seven hundred twenty-one".