66617813 has 4 divisors (see below), whose sum is σ = 66639948. Its totient is φ = 66595680.

The previous prime is 66617783. The next prime is 66617827. The reversal of 66617813 is 31871666.

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 26142769 + 40475044 = 5113^2 + 6362^2 .

It is a cyclic number.

It is not a de Polignac number, because 66617813 - 2¹² = 66613717 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 (66617833) 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, 5678 + ... + 12863.

It is an arithmetic number, because the mean of its divisors is an integer number (16659987).

Almost surely, 2^66617813 is an apocalyptic number.

It is an amenable number.

66617813 is a deficient number, since it is larger than the sum of its proper divisors (22135).

66617813 is a wasteful number, since it uses less digits than its factorization.

66617813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22134.

The product of its digits is 36288, while the sum is 38.

The square root of 66617813 is about 8161.9735971149. The cubic root of 66617813 is about 405.3810628783.

The spelling of 66617813 in words is "sixty-six million, six hundred seventeen thousand, eight hundred thirteen".