66688217 has 2 divisors, whose sum is σ = 66688218. Its totient is φ = 66688216.

The previous prime is 66688211. The next prime is 66688261. The reversal of 66688217 is 71288666.

It is an a-pointer prime, because the next prime (66688261) can be obtained adding 66688217 to its sum of digits (44).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41847961 + 24840256 = 6469^2 + 4984^2 .

It is a cyclic number.

It is not a de Polignac number, because 66688217 - 2⁸ = 66687961 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (66688211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33344108 + 33344109.

It is an arithmetic number, because the mean of its divisors is an integer number (33344109).

Almost surely, 2^66688217 is an apocalyptic number.

It is an amenable number.

66688217 is a deficient number, since it is larger than the sum of its proper divisors (1).

66688217 is an equidigital number, since it uses as much as digits as its factorization.

66688217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 193536, while the sum is 44.

The square root of 66688217 is about 8166.2853856573. The cubic root of 66688217 is about 405.5238194914.

The spelling of 66688217 in words is "sixty-six million, six hundred eighty-eight thousand, two hundred seventeen".