How to explode integer?

Hello. I'm programming Arduino in C and I want to know how to explode integer.... In PHP I just need to write:
$substring = explode($string, "");
please help me.

I tried to use:
charAt();

void setup() {
Serial.begin(9600);
}

void loop() {
int sensorValue = analogRead(A1);
analogWrite(A0, sensorValue);
int a = analogRead(A1);
String aa=(String)a;
int a1 = aa.charAt(1);
int a2 = aa.charAt(2);
int a3 = aa.charAt(3);
int a4 = aa.charAt(4);
Serial.println("char at 1:" + a1);
Serial.println("char at 2:" + a2);
Serial.println("char at 3:" + a3);
Serial.println("char at 4:" + a4);
Serial.println("");
Serial.println("sensor:" + sensorValue);
Serial.println("");
delay(1000);
}

but there was an error...it displays some crazy thigs in serial monitor :(


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please is there any other way to explode integer?

Thank you in advance.

Ohh. I found the bug, but it is not working :( It is displaying some crazy numbers:

char at 1:54
char at 2:48
char at 3:0
char at 4:0

sensor:659


this is new code:

void setup() {
Serial.begin(9600);
}

void loop() {
int sensorValue = analogRead(A1);
analogWrite(A0, sensorValue);
int a = analogRead(A1);
String aa=(String)a;
int a1 = aa.charAt(1);
int a2 = aa.charAt(2);
int a3 = aa.charAt(3);
int a4 = aa.charAt(4);
Serial.print("char at 1:"); Serial.println(a1);
Serial.print("char at 2:"); Serial.println(a2);
Serial.print("char at 3:"); Serial.println(a3);
Serial.print("char at 4:"); Serial.println(a4);
Serial.println("");
Serial.print("sensor:"); Serial.println(sensorValue);
Serial.println("");
delay(100);
}