iOS convert large numbers to smaller format

-(NSString*) suffixNumber:(NSNumber*)number
{
    if (!number)
        return @"";

    long long num = [number longLongValue];

    int s = ( (num < 0) ? -1 : (num > 0) ? 1 : 0 );
    NSString* sign = (s == -1 ? @"-" : @"" );

    num = llabs(num);

    if (num < 1000)
        return [NSString stringWithFormat:@"%@%lld",sign,num];

    int exp = (int) (log10l(num) / 3.f); //log10l(1000));

    NSArray* units = @[@"K",@"M",@"G",@"T",@"P",@"E"];

    return [NSString stringWithFormat:@"%@%.1f%@",sign, (num / pow(1000, exp)), [units objectAtIndex:(exp-1)]];
}

sample usage

NSLog(@"%@",[self suffixNumber:@100]); // 100
NSLog(@"%@",[self suffixNumber:@1000]); // 1.0K
NSLog(@"%@",[self suffixNumber:@1500]); // 1.5K
NSLog(@"%@",[self suffixNumber:@24000]); // 24.0K
NSLog(@"%@",[self suffixNumber:@99900]); // 99.9K
NSLog(@"%@",[self suffixNumber:@99999]); // 100.0K
NSLog(@"%@",[self suffixNumber:@109999]); // 110.0K
NSLog(@"%@",[self suffixNumber:@5109999]); // 5.1M
NSLog(@"%@",[self suffixNumber:@8465445223]); // 8.5G
NSLog(@"%@",[self suffixNumber:[NSNumber numberWithInt:-120]]); // -120
NSLog(@"%@",[self suffixNumber:[NSNumber numberWithLong:-5000000]]); // -5.0M
NSLog(@"%@",[self suffixNumber:[NSNumber numberWithDouble:-3.5f]]); // -3
NSLog(@"%@",[self suffixNumber:[NSNumber numberWithDouble:-4000.63f]]); // -4.0K

[Update]

Swift version below:

func suffixNumber(number:NSNumber) -> NSString {

    var num:Double = number.doubleValue;
    let sign = ((num < 0) ? "-" : "" );

    num = fabs(num);

    if (num < 1000.0){
        return "\(sign)\(num)";
    }

    let exp:Int = Int(log10(num) / 3.0 ); //log10(1000));

    let units:[String] = ["K","M","G","T","P","E"];

    let roundedNum:Double = round(10 * num / pow(1000.0,Double(exp))) / 10;

    return "\(sign)\(roundedNum)\(units[exp-1])";
}

sample usage

print(self.suffixNumber(NSNumber(long: 100))); // 100.0
print(self.suffixNumber(NSNumber(long: 1000))); // 1.0K
print(self.suffixNumber(NSNumber(long: 1500))); // 1.5K
print(self.suffixNumber(NSNumber(long: 24000))); // 24.0K
print(self.suffixNumber(NSNumber(longLong: 99900))); // 99.9K
print(self.suffixNumber(NSNumber(longLong: 99999))); // 100.0K
print(self.suffixNumber(NSNumber(longLong: 109999))); // 110.0K
print(self.suffixNumber(NSNumber(longLong: 5109999))); // 5.1K
print(self.suffixNumber(NSNumber(longLong: 8465445223))); // 8.5G
print(self.suffixNumber(NSNumber(long: -120))); // -120.0
print(self.suffixNumber(NSNumber(longLong: -5000000))); // -5.0M
print(self.suffixNumber(NSNumber(float: -3.5))); // -3.5
print(self.suffixNumber(NSNumber(float: -4000.63))); // -4.0K

Hope it helps