261457065640 has 32 divisors (see below), whose sum is σ = 588340459080. Its totient is φ = 104571793152.

The previous prime is 261457065563. The next prime is 261457065673. The reversal of 261457065640 is 46560754162.

It can be written as a sum of positive squares in 4 ways, for example, as 250842708964 + 10614356676 = 500842^2 + 103026^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44542 + ... + 724498.

Almost surely, 2^261457065640 is an apocalyptic number.

261457065640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261457065640 is an abundant number, since it is smaller than the sum of its proper divisors (326883393440).

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

261457065640 is a wasteful number, since it uses less digits than its factorization.

261457065640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 689581 (or 689577 counting only the distinct ones).

The product of its (nonzero) digits is 1209600, while the sum is 46.

The spelling of 261457065640 in words is "two hundred sixty-one billion, four hundred fifty-seven million, sixty-five thousand, six hundred forty".