Search a number
Duffinian n.  and  economical n.

First numbers that belong to both sets:

16, 21, 25, 27, 32, 35, 49, 64, 81, 111, 115, 119, 121, 125, 128, 129, 133, 155, 161, 169, 175, 183, 185, 189, 201, 203, 205, 215, 217, 219, 235, 237, 243, 245, 256, 259, 265, 289, 291, 301, 305, 329, 335, 343, 355, 361, 365, 371, 413, 415, 427, 469, 485, 497, 511, 512, 529, 553, 567, 623, 625, 729, 841, 875, 961, 1003, 1007, 1011, 1024, 1025, 1027, 1029, 1037, 1043, 1047, 1053, 1055, 1057, 1058, 1067, 1073, 1075, 1079, 1081, 1085, 1099, 1101, 1115, 1119, 1121, 1127, 1135, 1137, 1141, 1147, 1157, 1159, 1161, 1165, 1175, 1183, 1189, 1191, 1205, 1207, 1211, 1219, 1225, 1227, 1241, 1247, 1250, 1253, 1255, 1261, 1263, 1271, 1273, 1281, 1285, 1295, 1296, 1299, 1315, 1317, 1325, 1331, 1333, 1337, 1343, 1349, 1351, 1355, 1357, 1363, 1369, 1371, 1375, 1379, 1385, 1387, 1389, 1393, 1403, 1405, 1407, 1411, 1415, 1421, 1445, 1457, 1461, 1465, 1477, 1497, 1501, 1505, 1513, 1517, 1519, 1525, 1533, 1535, 1537, 1539, 1541, 1555, 1565, 1569, 1577, 1585, 1587, 1589, 1591, 1600, 1603, 1623, 1631, 1633, 1641, 1643, 1645, 1647, 1649, 1655, 1659, 1673, 1675, 1679, 1681, 1682, 1685, 1687, 1691, 1711, 1713, 1731, 1735, 1739, 1763, 1765, 1769, 1775, 1799, 1803, 1805, 1809, 1813, 1817, 1821, 1825, 1829, 1835, 1839, 1841, 1843, 1849, 1855, 1857, 1865, 1875, 1883, 1893, 1897, 1909, 1915, 1922, 1927, 1929, 1939, 1943, 1961, 1967, 1971, 1981, 1983, 1985, 2005, 2019, 2021, 2023, 2025, 2047, 2048, 2059, 2073, 2075, 2077, 2105, 2107, 2117, 2125, 2127, 2133, 2135, 2155, 2165, 2173, 2177, 2181, 2183, 2187, 2191, 2197, 2199, 2201, 2209, 2215, 2217, 2219, 2231, 2253, 2257, 2263, 2271, 2279, 2285, 2291, 2303, 2304.

Some larger examples :