261616271665 has 32 divisors (see below), whose sum is σ = 376005196800. Its totient is φ = 174545485632.

The previous prime is 261616271647. The next prime is 261616271699. The reversal of 261616271665 is 566172616162.

It is not a de Polignac number, because 261616271665 - 2³³ = 253026337073 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1997977 + ... + 2124886.

It is an arithmetic number, because the mean of its divisors is an integer number (11750162400).

Almost surely, 2^261616271665 is an apocalyptic number.

It is an amenable number.

261616271665 is a deficient number, since it is larger than the sum of its proper divisors (114388925135).

261616271665 is an equidigital number, since it uses as much as digits as its factorization.

261616271665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4122926 (or 4122912 counting only the distinct ones).

The product of its digits is 1088640, while the sum is 49.

The spelling of 261616271665 in words is "two hundred sixty-one billion, six hundred sixteen million, two hundred seventy-one thousand, six hundred sixty-five".