locale.formatPrefix(specifier, value)
Equivalent to locale.format, except the returned function will convert values to the units of the appropriate SI prefix for the specified numeric reference value before formatting in fixed point notation. The following prefixes are supported:
y - yocto, 10⁻²⁴
z - zepto, 10⁻²¹
a - atto, 10⁻¹⁸
f - femto, 10⁻¹⁵
p - pico, 10⁻¹²
n - nano, 10⁻⁹
µ - micro, 10⁻⁶
m - milli, 10⁻³
(none) - 10⁰
k - kilo, 10³
M - mega, 10⁶
G - giga, 10⁹
T - tera, 10¹²