Are there any OLTP databases that are able to replace the use of OLAP databases?

OLAP and OLTP databases have completely different architectural methodology and cater to different set of use cases.
OLTP is more suited for atomic transactional processing and emphasizes on optimizing storage of data and avoid anomalies.
OLAP on the other hand focuses on reporting and analytics and hence tries to ensure fastest retrieval and processing of huge amount of data for the analytical tools which would involve cleansing, transforming, aggregating etc kind of operations.
As such it doesn’t make sense to try to replace OLTP with OLAP based database or vice versa. Each of them has a definite purpose for which they need to be used for.