66515500561 has 4 divisors (see below), whose sum is σ = 70016316400. Its totient is φ = 63014684724.

The previous prime is 66515500553. The next prime is 66515500607. The reversal of 66515500561 is 16500551566.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66515500561 - 2³ = 66515500553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66515500511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1750407891 + ... + 1750407928.

It is an arithmetic number, because the mean of its divisors is an integer number (17504079100).

Almost surely, 2^66515500561 is an apocalyptic number.

It is an amenable number.

66515500561 is a deficient number, since it is larger than the sum of its proper divisors (3500815839).

66515500561 is a wasteful number, since it uses less digits than its factorization.

66515500561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3500815838.

The product of its (nonzero) digits is 135000, while the sum is 40.

The spelling of 66515500561 in words is "sixty-six billion, five hundred fifteen million, five hundred thousand, five hundred sixty-one".