2282281domain: NPropertiesPrimalityPrimeyesAppears in sequencesGeneralized Markoff numbers: union of numbers a, b, c, d satisfying the Markoff(4) equation a^2 + b^2 + c^2 + d^2 = 4*a*b*c*d.at n=25A075276Primes p at which phi(p-1)/(p-1) reaches a new minimum, where phi is Euler's totient function.at n=11A241196Prime numbersat n=168313