Give five children an average of four more, and then add one more, which can be divided equally.

On average, six children give five more, and then one more, which can be divided equally.

.....

If you add 1 persimmon,

It can be evenly distributed to five, six, seven or eight children.

It shows that as long as one more persimmon is added, the number of persimmons can be divisible by 5.6.7.8.

Ask at least a few.

The least common multiple of 5.6.7.8 is 420, excluding the added persimmons.

420- 1=4 19