261665577540625 has 24 divisors (see below), whose sum is σ = 327063798952128. Its totient is φ = 209330695350000.

The previous prime is 261665577540613. The next prime is 261665577540673. The reversal of 261665577540625 is 526045775566162.

It is a happy number.

It is not a de Polignac number, because 261665577540625 - 2²⁵ = 261665543986193 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 470256324 + ... + 470812426.

It is an arithmetic number, because the mean of its divisors is an integer number (13627658289672).

Almost surely, 2^{261665577540625} is an apocalyptic number.

261665577540625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

261665577540625 is a deficient number, since it is larger than the sum of its proper divisors (65398221411503).

261665577540625 is an frugal number, since it uses more digits than its factorization.

261665577540625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 706699 (or 706679 counting only the distinct ones).

The product of its (nonzero) digits is 635040000, while the sum is 67.

The spelling of 261665577540625 in words is "two hundred sixty-one trillion, six hundred sixty-five billion, five hundred seventy-seven million, five hundred forty thousand, six hundred twenty-five".