261666385 has 16 divisors (see below), whose sum is σ = 331148160. Its totient is φ = 197942400.

The previous prime is 261666373. The next prime is 261666409. The reversal of 261666385 is 583666162.

It is not a de Polignac number, because 261666385 - 2¹³ = 261658193 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54804 + ... + 59386.

It is an arithmetic number, because the mean of its divisors is an integer number (20696760).

Almost surely, 2^261666385 is an apocalyptic number.

It is an amenable number.

261666385 is a deficient number, since it is larger than the sum of its proper divisors (69481775).

261666385 is a wasteful number, since it uses less digits than its factorization.

261666385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5208.

The product of its digits is 311040, while the sum is 43.

The square root of 261666385 is about 16176.1053718131. The cubic root of 261666385 is about 639.6110796236.

The spelling of 261666385 in words is "two hundred sixty-one million, six hundred sixty-six thousand, three hundred eighty-five".