261665121 has 16 divisors (see below), whose sum is σ = 357120000. Its totient is φ = 170343888.

The previous prime is 261665111. The next prime is 261665123. The reversal of 261665121 is 121566162.

261665121 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 261665121 - 2¹³ = 261656929 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261665123) 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, 68500 + ... + 72218.

It is an arithmetic number, because the mean of its divisors is an integer number (22320000).

Almost surely, 2^261665121 is an apocalyptic number.

It is an amenable number.

261665121 is a deficient number, since it is larger than the sum of its proper divisors (95454879).

261665121 is a wasteful number, since it uses less digits than its factorization.

261665121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4268.

The product of its digits is 4320, while the sum is 30.

The square root of 261665121 is about 16176.0663017929. The cubic root of 261665121 is about 639.6100497247.

The spelling of 261665121 in words is "two hundred sixty-one million, six hundred sixty-five thousand, one hundred twenty-one".