261642504665 has 8 divisors (see below), whose sum is σ = 322456708680. Its totient is φ = 203656868352.

The previous prime is 261642504653. The next prime is 261642504709. The reversal of 261642504665 is 566405246162.

It can be written as a sum of positive squares in 4 ways, for example, as 33819577801 + 227822926864 = 183901^2 + 477308^2 .

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 261642504665 - 2⁴ = 261642504649 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 707141720 + ... + 707142089.

It is an arithmetic number, because the mean of its divisors is an integer number (40307088585).

Almost surely, 2^261642504665 is an apocalyptic number.

It is an amenable number.

261642504665 is a deficient number, since it is larger than the sum of its proper divisors (60814204015).

261642504665 is a wasteful number, since it uses less digits than its factorization.

261642504665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1414283851.

The product of its (nonzero) digits is 2073600, while the sum is 47.

The spelling of 261642504665 in words is "two hundred sixty-one billion, six hundred forty-two million, five hundred four thousand, six hundred sixty-five".