66561561500 has 48 divisors (see below), whose sum is σ = 166137666240. Its totient is φ = 22821105600.

The previous prime is 66561561499. The next prime is 66561561509. The reversal of 66561561500 is 516516566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66561561509) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9505295 + ... + 9512294.

It is an arithmetic number, because the mean of its divisors is an integer number (3461201380).

Almost surely, 2^66561561500 is an apocalyptic number.

It is an amenable number.

66561561500 is an abundant number, since it is smaller than the sum of its proper divisors (99576104740).

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

66561561500 is a wasteful number, since it uses less digits than its factorization.

66561561500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19017615 (or 19017603 counting only the distinct ones).

The product of its (nonzero) digits is 162000, while the sum is 41.

The spelling of 66561561500 in words is "sixty-six billion, five hundred sixty-one million, five hundred sixty-one thousand, five hundred".