261534331222561 has 8 divisors (see below), whose sum is σ = 263445975694440. Its totient is φ = 259622724935808.

The previous prime is 261534331222471. The next prime is 261534331222573. The reversal of 261534331222561 is 165222133435162.

It can be written as a sum of positive squares in 4 ways, for example, as 31729348360161 + 229804982862400 = 5632881^2 + 15159320^2 .

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 261534331222561 - 2⁴³ = 252738238200353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261534331522561) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4274875 + ... + 23266783.

It is an arithmetic number, because the mean of its divisors is an integer number (32930746961805).

Almost surely, 2^{261534331222561} is an apocalyptic number.

It is an amenable number.

261534331222561 is a deficient number, since it is larger than the sum of its proper divisors (1911644471879).

261534331222561 is a wasteful number, since it uses less digits than its factorization.

261534331222561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19092563.

The product of its digits is 1555200, while the sum is 46.

The spelling of 261534331222561 in words is "two hundred sixty-one trillion, five hundred thirty-four billion, three hundred thirty-one million, two hundred twenty-two thousand, five hundred sixty-one".