261646077761640 has 384 divisors, whose sum is σ = 1004923645689600. Its totient is φ = 58550169300480.

The previous prime is 261646077761633. The next prime is 261646077761669. The reversal of 261646077761640 is 46167770646162.

It is a happy number.

261646077761640 is a `hidden beast` number, since 2 + 6 + 1 + 6 + 4 + 6 + 0 + 7 + 7 + 7 + 616 + 4 + 0 = 666.

It is a Smith number, since the sum of its digits (63) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 6336804 + ... + 23737043.

It is an arithmetic number, because the mean of its divisors is an integer number (2616988660650).

Almost surely, 2^{261646077761640} is an apocalyptic number.

261646077761640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 261646077761640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (502461822844800).

261646077761640 is an abundant number, since it is smaller than the sum of its proper divisors (743277567927960).

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

261646077761640 is a wasteful number, since it uses less digits than its factorization.

261646077761640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30073914 (or 30073881 counting only the distinct ones).

The product of its (nonzero) digits is 85349376, while the sum is 63.

The spelling of 261646077761640 in words is "two hundred sixty-one trillion, six hundred forty-six billion, seventy-seven million, seven hundred sixty-one thousand, six hundred forty".