[[66]] is not prime (composite): [[2]] * [[3]] * [[11]]

Factor pairs: [[2]] * [[33]], [[3]] * [[22]], [[6]] * [[11]]

Prime neighborhood: [[53]], [[59]], [[61]], [[66]], [[67]], [[71]], [[73]]

Prime gap: 6 (interval [[61]] to [[67]])

Primes up to 66: [[2]], [[3]], [[5]], [[7]], [[11]], [[13]], [[17]], [[19]], [[23]], [[29]], [[31]], [[37]], [[41]], [[43]], [[47]], [[53]], [[59]], [[61]] (18 total).

[[66]] is not a centered hexagonal number.

The closest centered hexagonal numbers are [[61]] (index # [[5]]) and [[91]] (index # [[6]]).

First 20 centered hexagonal numbers: [[1]], [[7]], [[19]], [[37]], [[61]], [[91]], [[127]], [[169]], [[217]], [[271]], [[331]], [[397]], [[469]], [[547]], [[631]], [[721]], [[817]], [[919]], [[1027]], [[1141]].

[[hz/66]] is closest to [[C2]] at [[66]] Hz (+16 cents).

Note class: [[C]], Octave: [[octave/2]].

• [[square]]: 4356

• [[square root]]: 8.1240

• [[cube]]: 287496

• [[cube root]]: 4.0412

• [[natural log]] (ln): 4.1897

• [[base-10 log]] (log10): 1.8195

• [[base-2 log]] (log2): 6.0444