261666999 has 24 divisors (see below), whose sum is σ = 414086400. Its totient is φ = 157908240.

The previous prime is 261666983. The next prime is 261667013. The reversal of 261666999 is 999666162.

It is a happy number.

It is not a de Polignac number, because 261666999 - 2⁴ = 261666983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261626999) 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 23 ways as a sum of consecutive naturals, for example, 18132 + ... + 29190.

It is an arithmetic number, because the mean of its divisors is an integer number (17253600).

Almost surely, 2^261666999 is an apocalyptic number.

261666999 is a deficient number, since it is larger than the sum of its proper divisors (152419401).

261666999 is a wasteful number, since it uses less digits than its factorization.

261666999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11315 (or 11312 counting only the distinct ones).

The product of its digits is 1889568, while the sum is 54.

The square root of 261666999 is about 16176.1243504122. The cubic root of 261666999 is about 639.6115799055.

The spelling of 261666999 in words is "two hundred sixty-one million, six hundred sixty-six thousand, nine hundred ninety-nine".