Money Want to join the 401(k) millionaires club? Here’s 5 keys to retirement success December 7, 2018Arielle O’Shea, NerdWalletComments Off on Want to join the 401(k) millionaires club? Here’s 5 keys to retirement success At Fidelity Investments, which holds over 16.2 million 401(k) accounts, only 187,000 had balances of $1 million or more at the end of September.