66918217 has 4 divisors (see below), whose sum is σ = 67361536. Its totient is φ = 66474900.

The previous prime is 66918211. The next prime is 66918223. The reversal of 66918217 is 71281966.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is an interprime number because it is at equal distance from previous prime (66918211) and next prime (66918223).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66918217 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66918217.

It is not an unprimeable number, because it can be changed into a prime (66918211) 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, 221433 + ... + 221734.

It is an arithmetic number, because the mean of its divisors is an integer number (16840384).

Almost surely, 2^66918217 is an apocalyptic number.

It is an amenable number.

66918217 is a deficient number, since it is larger than the sum of its proper divisors (443319).

66918217 is a wasteful number, since it uses less digits than its factorization.

66918217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 443318.

The product of its digits is 36288, while the sum is 40.

The square root of 66918217 is about 8180.3555546199. The cubic root of 66918217 is about 405.9894862477.

The spelling of 66918217 in words is "sixty-six million, nine hundred eighteen thousand, two hundred seventeen".