261661521 has 32 divisors (see below), whose sum is σ = 411494400. Its totient is φ = 146162880.

The previous prime is 261661471. The next prime is 261661531. The reversal of 261661521 is 125166162.

261661521 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 261661521 - 2⁶ = 261661457 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (261661531) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17560 + ... + 28838.

It is an arithmetic number, because the mean of its divisors is an integer number (12859200).

Almost surely, 2^261661521 is an apocalyptic number.

It is an amenable number.

261661521 is a deficient number, since it is larger than the sum of its proper divisors (149832879).

261661521 is a wasteful number, since it uses less digits than its factorization.

261661521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11349.

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

The square root of 261661521 is about 16175.9550259019. The cubic root of 261661521 is about 639.6071164504.

The spelling of 261661521 in words is "two hundred sixty-one million, six hundred sixty-one thousand, five hundred twenty-one".