Education:

He was a schoolboy in the Secondary School, created by Vasil Aprilov in Gabrovo, and a student in the Sofia University (1929–1933), where he become Professor Georgi Nadjakov's PhD student in physics (1940)

Research:

He investigated solid state physics and metrological problems mainly

Professional experience:

Razum Andrejchin was Assistant Professor (05.04.1937–03.05.1946), Associate Professor (25.02.1947), Research Fellow (01.03.1950), Professor (1961) and Researcher (1967)

Sofia University appointed him to assistant position in physics (05.04.1937–1941) and in astronomy (1941–31.05.1946)

Razum Andrejchin was Deputy-Director of the Institute of Physics at the Bulgarian Academy of Sciences (1952–1957)

Up to be pensioned off (1976) Razum Andrejchin worked in the Institute of Solid State Physics at the Bulgarian Academy of Sciences

Teaching activities:

Razum Andrejchin lectured physics at the Russe High Technical School (1947–1949) and later on at the Sofia University (1950–1957).