﻿﻿﻿ Every Day Counts

Centred Square Prime Days

Age: 21,840 days
Date of birth
Your 38th Centred Square Prime Day is on
Monday
when you will be
21,841 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:

Next Prime Events
Day Age
Event
Year Age
04 Dec 2023
21,841
tomorrow
59
04 Dec 2023
21,841
tomorrow
59
14 Mar 2025
22,307
467
61
01 Aug 2025
22,447
607
61
02 Sep 2027
23,209
1,369
63
14 Oct 2027
23,251
1,411
63
02 Aug 2042
28,657
6,817
78
18 Jul 2046
30,103
8,263
82
21 Dec 2065
37,199
15,359
101
28 Nov 2071
39,367
17,527
107
30 Oct 2083
43,721
21,881
119
28 Mar 2097
48,619
26,779
133
24 Jul 2143
65,537
43,697
179
06 Sep 2238
100,279
78,439
274
26 Mar 2262
108,881
87,041
298
27 Dec 2322
131,071
109,231
358
19 Apr 7781
2,124,679
2,102,839
5817
Ordinal
Day Age
Date
Age
1st
5
21 Feb 1964
0
2nd
13
29 Feb 1964
0
3rd
41
28 Mar 1964
0
4th
61
17 Apr 1964
0
5th
113
08 Jun 1964
0
6th
181
15 Aug 1964
0
7th
313
25 Dec 1964
0
8th
421
12 Apr 1965
1
9th
613
21 Oct 1965
1
10th
761
18 Mar 1966
2
11th
1,013
25 Nov 1966
2
12th
1,201
01 Jun 1967
3
13th
1,301
09 Sep 1967
3
14th
1,741
22 Nov 1968
4
15th
1,861
22 Mar 1969
5
16th
2,113
29 Nov 1969
5
17th
2,381
24 Aug 1970
6
18th
2,521
11 Jan 1971
6
19th
3,121
02 Sep 1972
8
20th
3,613
07 Jan 1974
9
21st
4,513
25 Jun 1976
12
22nd
5,101
03 Feb 1978
13
23rd
7,321
03 Mar 1984
20
24th
8,581
15 Aug 1987
23
25th
9,661
30 Jul 1990
26
26th
9,941
06 May 1991
27
27th
10,513
28 Nov 1992
28
28th
12,641
26 Sep 1998
34
29th
13,613
25 May 2001
37
30th
14,281
24 Mar 2003
39
31st
14,621
27 Feb 2004
40
32nd
15,313
19 Jan 2006
41
33rd
16,381
22 Dec 2008
44
34th
19,013
07 Mar 2016
52
35th
19,801
04 May 2018
54
36th
20,201
08 Jun 2019
55
37th
21,013
28 Aug 2021
57
38th
21,841
04 Dec 2023
59
1
39th
23,981
13 Oct 2029
65
40th
24,421
27 Dec 2030
66
41st
26,681
05 Mar 2037
73