Nadja is the Serbian, Croatian, and German spelling of Nadya — Russian for "hope" — from nadezhda.
Nadja Auermann (born 1971) is the German supermodel. The 1928 surrealist novel Nadja by André Breton is a literary classic.
Nadja does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Nadja reduce to 3, The Communicator. This is a traditional interpretive system, not a factual claim about the name.