This site describes solve-engine as it is on main: 2.43.0, which npm does not have yet. npm installs 2.40.0, so a page may show an answer that version does not give yet.
BIGINT_PACKAGE
const BIGINT_PACKAGE: IEnginePackage;Defined in: packages/engine/src/packages/biginteger/BigIntPackage.ts:5
Arbitrary-precision integer literals (suffixed, e.g. 123n) that overflow a normal number without losing precision.