19 × 2¹²⁴⁶ + 1 is a prime number, with 378 digits

23021212743900667707968918399410045849356099811623267748051222257510357668366498041692253830017773377709790443201938079208634765669487630163163205784264613699116564900427496359880371443411578361292629152350838577028152051591712643680196200300046120018571921254148713283034730134012277294958274788913253838556620318193415866641708448795360303780609155833370465682072063617007617