A lower limit on the half-life T-1/2 of Ra-226 With respect to spontaneous fission has been measured at a level of 4 x 10(18) yr. The probability of Ra-226 spontaneous fission proved to be about 50 times less than the value expected from the known systematics relating the ratio of the alpha-decay and spontaneous-fission probabilities to the fissility parameter Z(2)/A. It has been shown that the probabilities of spontaneous fission, alpha decay, and cluster decay of 88 less than or equal to Z less than or equal to 100 even-even nuclei admit a unified systematization in terms of the difference of the Coulomb energy in the vicinity of the scission point, V-Coul, and decay energy Q.