How is a synchronous 214 rpm motor for a 50 Hz mains possible?
From the same wikipedia page:

Synchronous speed: $$N_S = \dfrac{2\cdot 60 ×f}{p}$$

Where:

\$N_S\$ is the synchronous revolutions per minute [rpm]

\$f\$ is the mains frequency in Hz or s-1;

\$p\$ is the number of poles in the machine, this is always an even number;

\$2\$ because magnetic poles always come in pairs (except for free energy projects, these apparently found a way to create monopoles ...);

\$60\$ because there are 60 seconds in a minute.

Notice that mains frequency is in cycles per second and the synchronous speed is in revolutions per minute. So you have to convert either the speed or the frequency for equal units.

Therefore:

$$p = \dfrac{2\cdot 60× f}{N_S} = \dfrac{2\cdot60×50}{214} \approx 28$$

The number of poles must be an even number: 28 and the speed must obviously be rounded to 214 rpm (214.2857142857143........).