C:\>perl -MMath::BigInt -le "push @ans, 6**25; push @ans, Math::BigInt
+->new(6)**25; push @ans, 6**Math::BigInt->new(25); push @ans, Math::B
+igInt->new(6)**Math::BigInt->new(25); print for @ans"
2.84302880299297e+019
28430288029929701376
28430288029929701376
28430288029929701376
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As ++tybalt89 pointed out, you need to convert before you do the exponentiation. But you don't actually have to convert both -- you can convert either the base or the exponent or both, and the BigInt math will work correctly