ARSE
Wed 15 Oct 2025
Centred Triangular Prime Days
Your 25th Centred Triangular Prime Day is on
Friday
24 October 2025
when you will be
16,381 days old
A centred triangular prime is a centred triangular number that is prime.
Centred triangular numbers are of the form
A centred triangular number is a centred figurate number that represents a triangle with a dot in the centre and all other dots surrounding the centre in successive triangular layers.
The figures for the first four centred triangular numbers are shown below:
Next Prime Events
Day Age
Event
Days Ahead
Year Age
Ordinal
Day Age
Date
Age
1st
19
0
2nd
31
0
3rd
109
0
4th
199
0
5th
409
1
6th
571
1
7th
631
1
8th
829
2
9th
1,489
4
10th
1,999
5
11th
2,341
6
12th
2,971
8
13th
3,529
9
14th
4,621
12
15th
4,789
13
16th
7,039
19
17th
7,669
20
18th
8,779
24
19th
9,721
26
20th
10,459
28
21st
10,711
29
22nd
13,681
37
23rd
14,851
40
24th
16,069
43
25th
16,381
44
1
26th
17,659
48
27th
20,011
54
28th
20,359
55
29th
23,251
63
30th
25,939
71
31st
27,541
75
32nd
29,191
79
33rd
29,611
81
34th
31,321
85
35th
34,429
94
36th
36,739
100
37th
40,099
109
38th
40,591
111
39th
42,589
116