66646674705661 has 4 divisors (see below), whose sum is σ = 66646733731900. Its totient is φ = 66646615679424.

The previous prime is 66646674705649. The next prime is 66646674705673. The reversal of 66646674705661 is 16650747664666.

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

It is an interprime number because it is at equal distance from previous prime (66646674705649) and next prime (66646674705673).

It can be written as a sum of positive squares in 2 ways, for example, as 630952205625 + 66015722500036 = 794325^2 + 8125006^2 .

It is a cyclic number.

It is not a de Polignac number, because 66646674705661 - 2⁵ = 66646674705629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66646674705161) 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, 27785766 + ... + 30088903.

It is an arithmetic number, because the mean of its divisors is an integer number (16661683432975).

Almost surely, 2^{66646674705661} is an apocalyptic number.

It is an amenable number.

66646674705661 is a deficient number, since it is larger than the sum of its proper divisors (59026239).

66646674705661 is a wasteful number, since it uses less digits than its factorization.

66646674705661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59026238.

The product of its (nonzero) digits is 1097349120, while the sum is 70.

The spelling of 66646674705661 in words is "sixty-six trillion, six hundred forty-six billion, six hundred seventy-four million, seven hundred five thousand, six hundred sixty-one".