Ezra 2:26 Kabbalah

בְּנֵ֤י הָרָמָה֙ וָגָ֔בַע שֵׁ֥שׁ מֵא֖וֹת עֶשְׂרִ֥ים וְאֶחָֽד׃ (ס)

The children of Ramah and Geba, six hundred twenty and one.

Read kabbalistic (mystical) interpretation of Ezra 2:26: and classical mystical sources.