how to get n digits of a given number?

Question

I have very large number. I have to operate first n digits from left.

Is there a command in Mathematica that will give n digits of a given number something like xxxxx[123456789, 5]=12345?

IntegerPart[N[number/10^n]]is generating internal errors.

Cast the number as a string, then find the substring over the desired length, finally casting back as a number again. ToExpression(StringPart(ToString(123456789),1;;5;;1)) — JMoravitz, Apr 05 '20 at 19:52

score 0 · Answer 1 · answered Apr 05 '20 at 19:43

0

Try RealDigits[].

N[2000!, 50]
RealDigits[N[2000!, 50], 10]

(*  3.3162750924506332411753933805763240382811172081058*10^5735  *)
(*  {{3, 3, 1, 6, 2, 7, 5, 0, 9, 2, 4, 5, 0, 6, 3, 3, 2, 4, 1, 1, 7, 5, 3, 9, 3, 3, 8, 0, 5, 7, 6, 3, 2, 4, 0, 3, 8, 2, 8, 1, 1, 1, 7, 2, 0,   8, 1, 0, 5, 8}, 5736}  *)

answered Apr 05 '20 at 19:43

Eric Towers

67,037

Thanks with your help I have figured out it – Selena Gurpinar Apr 05 '20 at 19:57
as FromDigits[RealDigits[N[k/10^125, 125], 10]] – Selena Gurpinar Apr 05 '20 at 19:57
IntegerPart[N[num/10^(IntegerLength[num]-n),n] work well provided n<IntegerLength[num] – Selena Gurpinar Apr 06 '20 at 20:32

how to get n digits of a given number?

1 Answers1