[format descriptor] radix r [s]

RRRS, R3RS: forces a number to be expressed in the radix r. r may be the symbol 'B (binary), 'O (octal), 'D (decimal), or 'X (hex). s must be a symbol, either 'E or 'S, indicating whether the radix prefix is to be expressed or suppressed, respectively. s defaults to 'E (expressed). If no radix modifier is specified then the default is decimal and the prefix is suppressed.

See also number->string.