Find Previous Prime Number

Find the largest prime number smaller than 100.

prevprime(100)

ans =
97

Find the largest prime numbers smaller than 1000, 10000, and 100000 by specifying the input as a vector.

v = [1000 10000 100000];
prevprime(v)

ans =
         997        9973       99991

Find Large Prime Number

When finding large prime numbers, return exact symbolic integers by using symbolic input. Further, if your input has 15 or more digits, then use quotation marks and wrap the number in sym to represent the number accurately. For more information, see Numeric to Symbolic Conversion.

Find a large prime number by using 10^sym(18).

prevprime(10^sym(18))

ans =
999999999999999989

Find the prime number previous to 823572345728582545 by using quotation marks.

prevprime(sym('823572345728582545'))

ans =
823572345728582543