Oh, dude, a 21-digit number is called a "21-digit number." I mean, it's not like they have a fancy name for every length of numbers, you know? Just count those digits and there you have it, a 21-digit number. Keep it simple, right?
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!
The value of a digit in a number is called its place value.
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.
digit
21 and 20
Just that - a 26-digit number. There is no special name for that.
a long number
A 400-digit number is typically referred to as a "400-digit number." In mathematics, numbers are categorized by their number of digits, such as single-digit numbers, double-digit numbers, triple-digit numbers, and so on. Therefore, a number with 400 digits would simply be called a "400-digit number."
21, for example.
It is called the digit.