261505300984640 has 56 divisors (see below), whose sum is σ = 622711161125352. Its totient is φ = 104601841018880.

The previous prime is 261505300984639. The next prime is 261505300984643. The reversal of 261505300984640 is 46489003505162.

It is a happy number.

261505300984640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 3797759078656 + 257707541905984 = 1948784^2 + 16053272^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261505300984643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 152734910 + ... + 154437570.

Almost surely, 2^{261505300984640} is an apocalyptic number.

261505300984640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261505300984640 is an abundant number, since it is smaller than the sum of its proper divisors (361205860140712).

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

261505300984640 is a wasteful number, since it uses less digits than its factorization.

261505300984640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2182635 (or 2182625 counting only the distinct ones).

The product of its (nonzero) digits is 6220800, while the sum is 53.

The spelling of 261505300984640 in words is "two hundred sixty-one trillion, five hundred five billion, three hundred million, nine hundred eighty-four thousand, six hundred forty".