66605615651561 has 16 divisors (see below), whose sum is σ = 77183154916224. Its totient is φ = 56294088580224.

The previous prime is 66605615651537. The next prime is 66605615651567. The reversal of 66605615651561 is 16515651650666.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66605615651561 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 66605615651561.

It is not an unprimeable number, because it can be changed into a prime (66605615651567) 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, 14636615 + ... + 18639788.

It is an arithmetic number, because the mean of its divisors is an integer number (4823947182264).

Almost surely, 2^{66605615651561} is an apocalyptic number.

It is an amenable number.

66605615651561 is a deficient number, since it is larger than the sum of its proper divisors (10577539264663).

66605615651561 is a wasteful number, since it uses less digits than its factorization.

66605615651561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33280400.

The product of its (nonzero) digits is 29160000, while the sum is 59.

The spelling of 66605615651561 in words is "sixty-six trillion, six hundred five billion, six hundred fifteen million, six hundred fifty-one thousand, five hundred sixty-one".