Red, 78 74 bytes

func[n][p: copy"kMGT"parse reverse n[any[3 skip insert(take p)]]reverse n]

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Takes the input as a string.

Red, 85 bytes

func[n][p: copy"kMGT"parse reverse n[any[3 skip ahead skip insert(take p)]]reverse n]

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Takes the input as a string.

Red, 78 bytes

func[n][i: 0 parse reverse n[any[3 skip insert(pick"kMGT"i: i + 1)]]reverse n]

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Takes the input as a string.

Input as integer (up to 2^32):

Red, 85 bytes

func[n][i: 0 parse reverse n: to""n[any[3 skip insert(pick"kMGT"i: i + 1)]]reverse n]

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Red, 78 74 bytes

func[n][p: copy"kMGT"parse reverse n[any[3 skip insert(take p)]]reverse n]

Try it online!

Takes the input as a string.

Red, 78 bytes

func[n][i: 0 parse reverse n[any[3 skip insert(pick"kMGT"i: i + 1)]]reverse n]

Try it online!

Takes the input as a string.

Input as integer (up to 2^32):

Red, 87 bytes

func[n][i: 0 n: reverse to""n
parse n[any[3 skip insert(pick"kMGT"i: i + 1)]]reverse n]

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Red, 78 bytes

func[n][i: 0 parse reverse n[any[3 skip insert(pick"kMGT"i: i + 1)]]reverse n]

Try it online!

Takes the input as a string.

Input as integer (up to 2^32):

Red, 85 bytes

func[n][i: 0 parse reverse n: to""n[any[3 skip insert(pick"kMGT"i: i + 1)]]reverse n]

Try it online!