How many Number 1 hits did Elvis Presley have?

21 according to this website

http://www.everyhit.com/mostnumber1s.html

In the USA, when people talk about a #1 hit they usually mean on the Billboard charts. Joel Whitburn the music historian claims that Elvis Presley had 18 #1 hits. But I actually count more than that if one looks at ALL the Billboard charts: Pop, Country-Western, R&B, and Easy Listening (but ignores other entities like Cash Box and RIAA).

Starting with "I Forgot To Remember To Forget"/"Mystery Train" at #1 on the BB Country-Western chart and ending with "Way Down"/"Pledgin My Love", also at #1 on the Country-Western chart and released just before Presley's death, I count 20 #1 hits.

There was even a posthumous #1 hit on the BB Country-Western chart for "Guitar Man"/"Faded Love", thanks to a remix by producer Felton Jarvis. That would bring the total to 21.

https://en.wikipedia.org/wiki/List_of_Elvis_Presley_hit_singles#Global_chart_list