# `e`

## Description

Returns Euler’s number `e`, a mathematical constant approximately equal to `2.718281828459045`. This value is limited to 15 decimal places.

## Syntax

```dataprime
{{ function_syntax }}
```

## Example

**Use case: Model exponential growth**

Use `e` in combination with logarithms and powers to calculate predictive growth models. In this example, we calculate the growth rate and then predict the value 10 hours into the future.

### Example data

```json
{
    "initial_value": 500,
    "current_value": 1000,
    "time_since_start_hours": 10
}
```

### Example query

```dataprime
create prediction_in_ten_hours from (initial_value * power(e(), growth_rate * (time_since_start_hours + 10)))
```

### Example output

```json
{
    "initial_value": 500,
    "current_value": 1000,
    "time_since_start_hours": 10,
    "growth_rate": 0.0693,
    "prediction_in_ten_hours": 1999.41
}
```