21/13

Interval information

Ratio	21/13
Factorization	3 × 7 × 13-1
Monzo	[0 1 0 1 0 -1⟩
Size in cents	830.2532¢
Name	tridecimal supraminor sixth
Color name	thuzo 6th, 3uz6
FJS name	[math]\text{M6}^{7}_{13}[/math]
Special properties	reduced
Tenney height (log2 nd)	8.09276
Weil height (log2 max(n, d))	8.78463
Wilson height (sopfr(nd))	23
Harmonic entropy (Shannon, [math]\sqrt{nd}[/math])	~4.2186 bits
[sound info]
Open this interval in xen-calc

21/13, the tridecimal supraminor sixth, is ca. 830 cents in size. It has a very good approximation in 13edo.

This interval is a ratio of two consecutive Fibonacci numbers, therefore it approximates the golden ratio, specifically acoustic phi. In this case, 21/13 is ~2.8 ¢ flat of the golden ratio.

See also

• 26/21 – its octave complement
• Gallery of just intervals