[[80]] is not prime (composite). Want proof? :)

Full prime factorization: [[2]] * [[2]] * [[2]] * [[2]] * [[5]]

Factor pairs:

[[80]] = [[2]] * [[40]]

[[80]] = [[4]] * [[20]]

[[80]] = [[5]] * [[16]]

[[80]] = [[8]] * [[10]]

Proper divisors: [[2]], [[4]], [[5]], [[8]], [[10]], [[16]], [[20]], [[40]]

Primes up to 80: [[2]], [[3]], [[5]], [[7]], [[11]], [[13]], [[17]], [[19]], [[23]], [[29]], [[31]], [[37]], [[41]], [[43]], [[47]], [[53]], [[59]], [[61]], [[67]], [[71]], [[73]], [[79]].

[[80]] 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/80]] is closest to [[D#2]] at [[80]] Hz (+49 cents).

Note class: [[D#]], Octave: [[octave/2]].

• [[square]]: 6400

• [[square root]]: 8.9443

• [[cube]]: 512000

• [[cube root]]: 4.3089

• [[natural log]] (ln): 4.3820

• [[base-10 log]] (log10): 1.9031

• [[base-2 log]] (log2): 6.3219