x1 is 1021 of x2 in dimension/aspect x3 (default is units).
Cf. grake, mitre, snidu, stero, delno, molro, kelvo, xampo, gradu, litce, merli, centi, decti, dekto, femti, gigdo, gocti, gotro, kilto, megdo, mikri, milti, nanvi, petso, picti, terto, xatsi, xecto, xexso, zepti.