261665710456517 has 4 divisors (see below), whose sum is σ = 261665774368800. Its totient is φ = 261665646544236.

The previous prime is 261665710456459. The next prime is 261665710456561. The reversal of 261665710456517 is 715654017566162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 261665710456517 - 2⁴⁴ = 244073524412101 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 261665710456517.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261665713456517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25361267 + ... + 34154432.

It is an arithmetic number, because the mean of its divisors is an integer number (65416443592200).

Almost surely, 2^{261665710456517} is an apocalyptic number.

It is an amenable number.

261665710456517 is a deficient number, since it is larger than the sum of its proper divisors (63912283).

261665710456517 is an equidigital number, since it uses as much as digits as its factorization.

261665710456517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63912282.

The product of its (nonzero) digits is 63504000, while the sum is 62.

The spelling of 261665710456517 in words is "two hundred sixty-one trillion, six hundred sixty-five billion, seven hundred ten million, four hundred fifty-six thousand, five hundred seventeen".