As in Excel Help:
Excel has 15-digit limit Regardless of the number of digits displayed, Excel stores numbers with up to 15 digits of precision. If a number contains more than 15 significant digits, Excel converts the extra digits to zeros (0).
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And VFP has 16 digits of precision.

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Could you tell more about what are you doing and why do you need such a precision? See if it is appropriate to store numbers as text:

CREATE CURSOR irepo (fld1 n(16), fld2 c(16))
ln=4568150590713391

INSERT INTO irepo VALUES (ln+recn(),TRANSFORM(ln+recno()))
INSERT INTO irepo VALUES (ln+recn(),TRANSFORM(ln+recno()))

copy to c:\yy xls



>yes but now that instruccion put into excel 4568150590713390
>but is this 4568150590713391