261686537784 has 128 divisors (see below), whose sum is σ = 879618700800. Its totient is φ = 70369482240.

The previous prime is 261686537771. The next prime is 261686537867. The reversal of 261686537784 is 487735686162.

261686537784 is a `hidden beast` number, since 2 + 6 + 16 + 8 + 6 + 537 + 7 + 84 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5064682 + ... + 5116089.

It is an arithmetic number, because the mean of its divisors is an integer number (6872021100).

Almost surely, 2^261686537784 is an apocalyptic number.

261686537784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

261686537784 is an abundant number, since it is smaller than the sum of its proper divisors (617932163016).

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

261686537784 is a wasteful number, since it uses less digits than its factorization.

261686537784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10180810 (or 10180800 counting only the distinct ones).

The product of its digits is 81285120, while the sum is 63.

The spelling of 261686537784 in words is "two hundred sixty-one billion, six hundred eighty-six million, five hundred thirty-seven thousand, seven hundred eighty-four".