66605881521 has 16 divisors (see below), whose sum is σ = 88952460480. Its totient is φ = 44331672000.

The previous prime is 66605881519. The next prime is 66605881541. The reversal of 66605881521 is 12518850666.

It is not a de Polignac number, because 66605881521 - 2¹ = 66605881519 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66605881501) 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, 5430646 + ... + 5442896.

It is an arithmetic number, because the mean of its divisors is an integer number (5559528780).

Almost surely, 2^66605881521 is an apocalyptic number.

It is an amenable number.

66605881521 is a deficient number, since it is larger than the sum of its proper divisors (22346578959).

66605881521 is a wasteful number, since it uses less digits than its factorization.

66605881521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15056.

The product of its (nonzero) digits is 691200, while the sum is 48.

The spelling of 66605881521 in words is "sixty-six billion, six hundred five million, eight hundred eighty-one thousand, five hundred twenty-one".