145.5 million SSNs + name and addresses DoBs and in many cases driver's licenses and credit card numbers were compromised.
Equifax and the forensic security company hired determined it was impossible to confirm every SSN breached but apparently 145.5 million SSNs were in the databases breached.
Rough napkin math (based on census estimates) says there are around 200m people over the age of 18 in the US in 2017