261687909 has 16 divisors (see below), whose sum is σ = 412513920. Its totient is φ = 144379200.

The previous prime is 261687901. The next prime is 261687913. The reversal of 261687909 is 909786162.

261687909 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 261687909 - 2³ = 261687901 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261687901) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 214242 + ... + 215459.

It is an arithmetic number, because the mean of its divisors is an integer number (25782120).

Almost surely, 2^261687909 is an apocalyptic number.

261687909 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

261687909 is a deficient number, since it is larger than the sum of its proper divisors (150826011).

261687909 is a wasteful number, since it uses less digits than its factorization.

261687909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429740.

The product of its (nonzero) digits is 326592, while the sum is 48.

The square root of 261687909 is about 16176.7706604254. The cubic root of 261687909 is about 639.6286167270.

It can be divided in two parts, 2616 and 87909, that added together give a triangular number (90525 = T₄₂₅).

The spelling of 261687909 in words is "two hundred sixty-one million, six hundred eighty-seven thousand, nine hundred nine".