Every Day Counts
Centred Square Prime Days
 
Age: 19,802 days
Date of birth
Your 36th Centred Square Prime Day is on
Saturday
when you will be
20,201 days old

A centred square prime is a centred square number that is prime.

Unlike regular square numbers, which are never prime, quite a few of the centred square numbers are prime.

Centred square numbers are of the form n2 + (n - 1)2

In elementary number theory, a centred square number is a centred figurate number that gives the number of dots in a square with a dot in the centre and all other dots surrounding the centre dot in successive square layers. That is, each centred square number equals the number of dots within a given city block distance of the centre dot on a regular square lattice. While centred square numbers, like figurate numbers in general, have few if any direct practical applications, they are sometimes studied in recreational mathematics for their elegant geometric and arithmetic properties.

The figures for the first four centred square numbers are shown below:

Remind me, please


Next Prime Events
Day Age
Event
Days Ahead
Year Age
11 Nov 2020
19,813
11
54
28 Jan 2021
19,891
89
54
05 Mar 2021
19,927
125
54
15 Mar 2021
19,937
135
54
15 Mar 2021
19,937
135
54
28 May 2021
20,011
209
54
04 Dec 2021
20,201
399
55
09 May 2022
20,357
555
55
28 Jan 2045
28,657
8,855
78
26 May 2074
39,367
19,565
107
27 Apr 2086
43,721
23,919
119
24 Sep 2099
48,619
28,817
133
19 Jan 2146
65,537
45,735
179
04 Mar 2241
100,279
80,477
274
21 Sep 2264
108,881
89,079
298
24 Jun 2325
131,071
111,269
358
16 Oct 7783
2,124,679
2,104,877
5817
Ordinal
Day Age
Date
Age
1st
5
19 Aug 1966
0
2nd
13
27 Aug 1966
0
3rd
41
24 Sep 1966
0
4th
61
14 Oct 1966
0
5th
113
05 Dec 1966
0
6th
181
11 Feb 1967
0
7th
313
23 Jun 1967
0
8th
421
09 Oct 1967
1
9th
613
18 Apr 1968
1
10th
761
13 Sep 1968
2
11th
1,013
23 May 1969
2
12th
1,201
27 Nov 1969
3
13th
1,301
07 Mar 1970
3
14th
1,741
21 May 1971
4
15th
1,861
18 Sep 1971
5
16th
2,113
27 May 1972
5
17th
2,381
19 Feb 1973
6
18th
2,521
09 Jul 1973
6
19th
3,121
01 Mar 1975
8
20th
3,613
05 Jul 1976
9
21st
4,513
22 Dec 1978
12
22nd
5,101
01 Aug 1980
13
23rd
7,321
30 Aug 1986
20
24th
8,581
10 Feb 1990
23
25th
9,661
25 Jan 1993
26
26th
9,941
01 Nov 1993
27
27th
10,513
27 May 1995
28
28th
12,641
24 Mar 2001
34
29th
13,613
21 Nov 2003
37
30th
14,281
19 Sep 2005
39
31st
14,621
25 Aug 2006
40
32nd
15,313
17 Jul 2008
41
33rd
16,381
20 Jun 2011
44
34th
19,013
03 Sep 2018
52
35th
19,801
30 Oct 2020
54
36th
20,201
04 Dec 2021
55
1
37th
21,013
24 Feb 2024
57
38th
21,841
01 Jun 2026
59
39th
23,981
10 Apr 2032
65
40th
24,421
24 Jun 2033
66
41st
26,681
01 Sep 2039
73