How many Scouts Cubs and Beavers are there in the world?

There is no good answer here. Totals reported by the international associations are not broken down by age and age based sections in the national Scout and Guide organizations vary quite a bit.

For example, in the Scout Association in the UK, sections are:

• Beaver Scouts- 6 to 8 years
• Cub Scouts- 8 to 101⁄2 years
• Scouts- 101⁄2 to 14 years
• Explorer Scouts- 14 to 18 years

In the Boy Scouts of America, divisions are:

• Cub Scouting- boys from first to fifth-grade or 5 to 11 years.
• Boy Scouting- boys ages 10 to 18
  • Varsity Scouting- boys ages 14 to 18
• Venturing- ages 13 through 21
  • Sea Scouting- 13 through 21