66666997 has 4 divisors (see below), whose sum is σ = 66713260. Its totient is φ = 66620736.

The previous prime is 66666983. The next prime is 66667037. The reversal of 66666997 is 79966666.

It is a happy number.

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 29224836 + 37442161 = 5406^2 + 6119^2 .

It is a cyclic number.

It is not a de Polignac number, because 66666997 - 2⁷ = 66666869 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 (66666937) 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, 20898 + ... + 23875.

It is an arithmetic number, because the mean of its divisors is an integer number (16678315).

Almost surely, 2^66666997 is an apocalyptic number.

It is an amenable number.

66666997 is a deficient number, since it is larger than the sum of its proper divisors (46263).

66666997 is a wasteful number, since it uses less digits than its factorization.

66666997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46262.

The product of its digits is 4408992, while the sum is 55.

The square root of 66666997 is about 8164.9860379550. The cubic root of 66666997 is about 405.4808027551.

The spelling of 66666997 in words is "sixty-six million, six hundred sixty-six thousand, nine hundred ninety-seven".