Ranges

<?php

$num = 15623;
$part_length = 1476;

$parts = $num / $part_length;

for ($i = 0; $i < $parts; $i++) {
    $start = $i*$part_length;
    $end = $start + $part_length;
    
    $ranges[] = [$start+1, $end];
}

if ($num % $part_length) $ranges[count($ranges)-1][1] = $num;

foreach ($ranges as $range) {
    echo "${range[0]}:${range[1]}\n";
}