It is called a 28-digit number!
A 1000-digit number is called a "millidigit" number. The prefix "milli-" denotes one thousandth, so a millidigit number is a number consisting of 1000 digits. In the realm of mathematics, such large numbers are often encountered in fields like cryptography, number theory, and computer science.
Just that - a 26-digit number. There is no special name for that.
Rounding to the first digit is simply called rounding. This will make the number equal to the same as what the number truly is.
A number that has more than one digit is called a "multi-digit number." In mathematics, a digit is a single symbol used to represent numbers (0-9). Therefore, a number with two or more of these symbols is considered a multi-digit number. These numbers can be broken down into individual place values, such as units, tens, hundreds, and so on.
100 quintillion is a 21 digit number with 20 zeroes.
It is called a 28-digit number!
It is called a twelve-digit number. Its exact name will depend on the number.
I suggest you just call it that - a "35-digit number".
The value of a digit in a number is called its place value.
21 and 20
We generally refer to them by the number of digits. Two-digit number, three-digit number, etc.
A 1000-digit number is called a "millidigit" number. The prefix "milli-" denotes one thousandth, so a millidigit number is a number consisting of 1000 digits. In the realm of mathematics, such large numbers are often encountered in fields like cryptography, number theory, and computer science.
21, for example.
Just that - a 26-digit number. There is no special name for that.
digit
a long number