<human>:  Who discovered the Riemann zeta function in complex analysis?
<bot>: The Riemann zeta function is named after Bernhard Riemann, who first studied it in 1859. Riemann discovered that the zeta function is related to the prime numbers, which are the numbers that are divisible only by themselves and 1. In fact, the Riemann zeta function is the only function that is defined everywhere on the complex plane, except at 0.