66515556566 has 8 divisors (see below), whose sum is σ = 105642354600. Its totient is φ = 31301438368.

The previous prime is 66515556521. The next prime is 66515556589. The reversal of 66515556566 is 66565551566.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 978169916 + ... + 978169983.

It is an arithmetic number, because the mean of its divisors is an integer number (13205294325).

Almost surely, 2^66515556566 is an apocalyptic number.

66515556566 is a deficient number, since it is larger than the sum of its proper divisors (39126798034).

66515556566 is a wasteful number, since it uses less digits than its factorization.

66515556566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1956339918.

The product of its digits is 24300000, while the sum is 56.

Subtracting 66515556566 from its reverse (66565551566), we obtain a triangular number (49995000 = T₉₉₉₉).

The spelling of 66515556566 in words is "sixty-six billion, five hundred fifteen million, five hundred fifty-six thousand, five hundred sixty-six".