Glitches are common phenomena in pulsars. After each glitch, there is often a permanent increase in the pulsar's spin-down rate. Therefore, a pulsar's present spin-down rate may be much higher than its initial value and the characteristic age of a pulsar based on its present spin-down rate and period may be shorter than its true age. At the same time, the permanent increase of its spin-down rate implies that the pulsar's surface magnetic field is increased after each glitch. Consequently, after many glitches some radio pulsars may evolve into magnetars, i.e., strongly magnetized and slowly rotating neutron stars.