# Primo

Workload type |
ECPP |

First release |
2001-08-03 |

Latest version |
4.3.1 2019-04-28 |

**Primo** is a computer program which tests numbers for primality using the Elliptic Curve Primality Proving (ECPP) algorithm, the fastest known general-purpose primality testing algorithm. Primo is developed by Marcel Martin using Free Pascal and Lazarus IDE.

The program does not require a number to be of any specific form. If a number is found to be prime, a primality certificate is produced, which can be quickly verified.

The record largest prime certified using Primo (as of April 2018) is 2^{116224}-15905. It has 34,987 digits. The certification of this number was done by Peter Kaiser with Primo 4.1.1. The certification process took 694 days for the phase 1 and 58 days for the phase 2 using a Dual Intel E2667 processor (16 cores at 3.2 GHz).

The Factoring Database allows users to upload Primo certificates.

## See also

- ECPP-DJ - an open-source implementation of ECPP test, which can also verify certificates generated by Primo.