user21128: How can I store a 13 digits int in Arduino?
For example, current timestamp is: 
1500666822235
An uint32_t can only hold 10 digits max.
64 bits integer does not seem to be supported on RFduino.

user30005: 
How can I store a 13 digits int in Arduino?

create a multi-byte type.
a 40-bit (32+8 bits), or a 96-bit (32+32+32) would hold a ton.
or BCD.

user30198: 18446744073709551615
That 20 digits. It is the maximum value of a uint64_t. Even the Arduino Uno can use the uint64_t. Perhaps the Serial.print does not support it, but the compiler supports it.
Which processor does your RFduino have ?
Where does the timestamp come from ? Perhaps you are asking the wrong question. Perhaps this is a xy-problem.

21128: <p>How can I store a 13 digits int in Arduino?</p>

<p>For example, current timestamp is: 
1500666822235</p>

<p>An uint32_t can only hold 10 digits max.</p>

<p>64 bits integer does not seem to be supported on RFduino.</p>
 30005: <blockquote>
  <p>How can I store a 13 digits int in Arduino?</p>
</blockquote>

<p>create a multi-byte type.</p>

<p>a 40-bit (32+8 bits), or a 96-bit (32+32+32) would hold a ton.</p>

<p>or BCD.</p>
 30198: <p><strong>18446744073709551615</strong><br>
That 20 digits. It is the maximum value of a <code>uint64_t</code>. Even the Arduino Uno can use the <code>uint64_t</code>. Perhaps the <code>Serial.print</code> does not support it, but the compiler supports it.</p>

<p>Which processor does your RFduino have ?</p>

<p>Where does the timestamp come from ? Perhaps you are asking the wrong question. Perhaps this is a <a href="http://xyproblem.info/" rel="noreferrer">xy-problem</a>.</p>
