Numbers in the Ethereum blockchain are represented by integers. Currently floating point numbers are not supported. The “natural unit” is the basic integer that represents a number.

• 1 ETH Natural Units
• 2 Token Natural Units
• 3 Source
• 4 See Also on BitcoinWiki

ETH Natural Units

ETH, or ethers, are represented by a natural unit with 18 decimal places.

1 ETH = 1,000,000,000,000,000,000 or 10^18 natural units. The ETH natural unit is also called a wei.

Token Natural Units

ERC20 tokens on the Ethereum blockchain also have a natural unit where 1 unit of token is represented by {x} natural units. This is represented by the decimal variable commonly written into the token smart contract. See Ethereum Based Tokens for further information.

For example:

• DGDb and UNI both have 0 decimal places, where 1 unit of token is represented by 1 natural unit.
• REP, GNT and many others have 18 decimal places, where 1 unit of token is represented by 1,000,000,000,000,000,000 or 10^18 natural units.

Source

http://theethereum.wiki/

See Also on BitcoinWiki

• Generating primes
• Block weight
• SIMD (hash function)
• Verifiable random function
• Common Scrambling Algorithm