66515556577 has 4 divisors (see below), whose sum is σ = 66519525376. Its totient is φ = 66511587780.

The previous prime is 66515556521. The next prime is 66515556589. The reversal of 66515556577 is 77565551566.

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, and also an emirpimes, since its reverse is a distinct semiprime: 77565551566 = 2 ⋅38782775783.

It is a cyclic number.

It is not a de Polignac number, because 66515556577 - 2⁷ = 66515556449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66515526577) 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, 1959153 + ... + 1992814.

It is an arithmetic number, because the mean of its divisors is an integer number (16629881344).

Almost surely, 2^66515556577 is an apocalyptic number.

It is an amenable number.

66515556577 is a deficient number, since it is larger than the sum of its proper divisors (3968799).

66515556577 is a wasteful number, since it uses less digits than its factorization.

66515556577 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3968798.

The product of its digits is 33075000, while the sum is 58.

The spelling of 66515556577 in words is "sixty-six billion, five hundred fifteen million, five hundred fifty-six thousand, five hundred seventy-seven".