9090901domain: NPropertiesPrimalityPrimeyesAppears in sequencesSmallest n-digit number m such that phi(10^n+1)=phi(m), gcd(10^n+1,m)=1 and 10 does not divide m, or zero if there is no such m.at n=6A147547Primes formed by concatenating n, n, n, and 1 for n = 1, 2, 3,....at n=25A210712Prime numbersat n=608113