66820669784065 has 4 divisors (see below), whose sum is σ = 80184803740884. Its totient is φ = 53456535827248.

The previous prime is 66820669784059. The next prime is 66820669784107. The reversal of 66820669784065 is 56048796602866.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20527124691969 + 46293545092096 = 4530687^2 + 6803936^2 .

It is a cyclic number.

It is not a de Polignac number, because 66820669784065 - 2²³ = 66820661395457 is a prime.

It is a Duffinian 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, 6682066978402 + ... + 6682066978411.

It is an arithmetic number, because the mean of its divisors is an integer number (20046200935221).

Almost surely, 2^{66820669784065} is an apocalyptic number.

It is an amenable number.

66820669784065 is a deficient number, since it is larger than the sum of its proper divisors (13364133956819).

66820669784065 is a wasteful number, since it uses less digits than its factorization.

66820669784065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13364133956818.

The product of its (nonzero) digits is 1254113280, while the sum is 73.

The spelling of 66820669784065 in words is "sixty-six trillion, eight hundred twenty billion, six hundred sixty-nine million, seven hundred eighty-four thousand, sixty-five".