261331604521 has 8 divisors (see below), whose sum is σ = 282555290304. Its totient is φ = 240268098000.

The previous prime is 261331604497. The next prime is 261331604537. The reversal of 261331604521 is 125406133162.

261331604521 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 261331604521 - 2¹⁷ = 261331473449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261331604551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40041421 + ... + 40047946.

It is an arithmetic number, because the mean of its divisors is an integer number (35319411288).

Almost surely, 2^261331604521 is an apocalyptic number.

It is an amenable number.

261331604521 is a deficient number, since it is larger than the sum of its proper divisors (21223685783).

261331604521 is a wasteful number, since it uses less digits than its factorization.

261331604521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80089631.

The product of its (nonzero) digits is 25920, while the sum is 34.

Adding to 261331604521 its reverse (125406133162), we get a palindrome (386737737683).

The spelling of 261331604521 in words is "two hundred sixty-one billion, three hundred thirty-one million, six hundred four thousand, five hundred twenty-one".