261666515541615 has 8 divisors (see below), whose sum is σ = 418666424866608. Its totient is φ = 139555474955520.

The previous prime is 261666515541577. The next prime is 261666515541679. The reversal of 261666515541615 is 516145515666162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261666515541615 - 2⁴⁷ = 120929027186287 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8722217184706 + ... + 8722217184735.

It is an arithmetic number, because the mean of its divisors is an integer number (52333303108326).

Almost surely, 2^{261666515541615} is an apocalyptic number.

261666515541615 is a deficient number, since it is larger than the sum of its proper divisors (156999909324993).

261666515541615 is a wasteful number, since it uses less digits than its factorization.

261666515541615 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17444434369449.

The product of its digits is 38880000, while the sum is 60.

The spelling of 261666515541615 in words is "two hundred sixty-one trillion, six hundred sixty-six billion, five hundred fifteen million, five hundred forty-one thousand, six hundred fifteen".