66561801750765 has 16 divisors (see below), whose sum is σ = 118332092001600. Its totient is φ = 35499627600336.

The previous prime is 66561801750709. The next prime is 66561801750811. The reversal of 66561801750765 is 56705710816566.

It is a happy number.

66561801750765 is a `hidden beast` number, since 6 + 6 + 5 + 61 + 8 + 0 + 1 + 7 + 507 + 65 = 666.

It is not a de Polignac number, because 66561801750765 - 2¹³ = 66561801742573 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 246525191535 + ... + 246525191804.

It is an arithmetic number, because the mean of its divisors is an integer number (7395755750100).

Almost surely, 2^{66561801750765} is an apocalyptic number.

It is an amenable number.

66561801750765 is a deficient number, since it is larger than the sum of its proper divisors (51770290250835).

66561801750765 is a wasteful number, since it uses less digits than its factorization.

66561801750765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 493050383353 (or 493050383347 counting only the distinct ones).

The product of its (nonzero) digits is 63504000, while the sum is 63.

The spelling of 66561801750765 in words is "sixty-six trillion, five hundred sixty-one billion, eight hundred one million, seven hundred fifty thousand, seven hundred sixty-five".