261543072661540 has 12 divisors (see below), whose sum is σ = 549240452589276. Its totient is φ = 104617229064608.

The previous prime is 261543072661517. The next prime is 261543072661631. The reversal of 261543072661540 is 45166270345162.

It can be written as a sum of positive squares in 2 ways, for example, as 177900963554304 + 83642109107236 = 13337952^2 + 9145606^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6538576816519 + ... + 6538576816558.

It is an arithmetic number, because the mean of its divisors is an integer number (45770037715773).

Almost surely, 2^{261543072661540} is an apocalyptic number.

261543072661540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261543072661540 is an abundant number, since it is smaller than the sum of its proper divisors (287697379927736).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261543072661540 is a wasteful number, since it uses less digits than its factorization.

261543072661540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13077153633086 (or 13077153633084 counting only the distinct ones).

The product of its (nonzero) digits is 7257600, while the sum is 52.

The spelling of 261543072661540 in words is "two hundred sixty-one trillion, five hundred forty-three billion, seventy-two million, six hundred sixty-one thousand, five hundred forty".