Banned for not having this memorized:
In number theory, Skewes' number is any of several extremely large numbers used by the South African mathematician Stanley Skewes as upper bounds for the smallest natural number x for which
\pi(x) > \operatorname{li}(x),
where π is the prime-counting function and li is the logarithmic integral function. These bounds have since been improved by others: there is a crossing near e^{727.95133}. It is not known whether it is the smallest.
In number theory, Skewes' number is any of several extremely large numbers used by the South African mathematician Stanley Skewes as upper bounds for the smallest natural number x for which
\pi(x) > \operatorname{li}(x),
where π is the prime-counting function and li is the logarithmic integral function. These bounds have since been improved by others: there is a crossing near e^{727.95133}. It is not known whether it is the smallest.