261371665 has 8 divisors (see below), whose sum is σ = 314475840. Its totient is φ = 208544112.

The previous prime is 261371647. The next prime is 261371713. The reversal of 261371665 is 566173162.

261371665 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 261371665 - 2²⁷ = 127153937 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 67069 + ... + 70858.

It is an arithmetic number, because the mean of its divisors is an integer number (39309480).

Almost surely, 2^261371665 is an apocalyptic number.

It is an amenable number.

261371665 is a deficient number, since it is larger than the sum of its proper divisors (53104175).

261371665 is a wasteful number, since it uses less digits than its factorization.

261371665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138311.

The product of its digits is 45360, while the sum is 37.

The square root of 261371665 is about 16166.9930723063. The cubic root of 261371665 is about 639.3708538943.

The spelling of 261371665 in words is "two hundred sixty-one million, three hundred seventy-one thousand, six hundred sixty-five".