﻿﻿﻿ Every Day Counts

Centred Square Prime Days

Age: 20,448 days
Date of birth
Your 37th Centred Square Prime Day is on
Tuesday
when you will be
21,013 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
19 Apr 2019
20,477
29
56
06 Oct 2020
21,013
565
57
11 Oct 2021
21,383
935
58
25 Aug 2022
21,701
1,253
59
09 Sep 2024
22,447
1,999
61
22 Nov 2026
23,251
2,803
63
10 Sep 2041
28,657
8,209
78
26 Aug 2045
30,103
9,655
82
29 Jan 2065
37,199
16,751
101
06 Jan 2071
39,367
18,919
107
08 Dec 2082
43,721
23,273
119
06 May 2096
48,619
28,171
133
01 Sep 2142
65,537
45,089
179
15 Oct 2237
100,279
79,831
274
04 May 2261
108,881
88,433
298
04 Feb 2322
131,071
110,623
358
28 May 7780
2,124,679
2,104,231
5817
Ordinal
Day Age
Date
Age
1st
5
01 Apr 1963
0
2nd
13
09 Apr 1963
0
3rd
41
07 May 1963
0
4th
61
27 May 1963
0
5th
113
18 Jul 1963
0
6th
181
24 Sep 1963
0
7th
313
03 Feb 1964
0
8th
421
21 May 1964
1
9th
613
29 Nov 1964
1
10th
761
26 Apr 1965
2
11th
1,013
03 Jan 1966
2
12th
1,201
10 Jul 1966
3
13th
1,301
18 Oct 1966
3
14th
1,741
01 Jan 1968
4
15th
1,861
30 Apr 1968
5
16th
2,113
07 Jan 1969
5
17th
2,381
02 Oct 1969
6
18th
2,521
19 Feb 1970
6
19th
3,121
12 Oct 1971
8
20th
3,613
15 Feb 1973
9
21st
4,513
04 Aug 1975
12
22nd
5,101
14 Mar 1977
13
23rd
7,321
12 Apr 1983
20
24th
8,581
23 Sep 1986
23
25th
9,661
07 Sep 1989
26
26th
9,941
14 Jun 1990
27
27th
10,513
07 Jan 1992
28
28th
12,641
04 Nov 1997
34
29th
13,613
03 Jul 2000
37
30th
14,281
02 May 2002
39
31st
14,621
07 Apr 2003
40
32nd
15,313
27 Feb 2005
41
33rd
16,381
31 Jan 2008
44
34th
19,013
16 Apr 2015
52
35th
19,801
12 Jun 2017
54
36th
20,201
17 Jul 2018
55
37th
21,013
06 Oct 2020
57
1
38th
21,841
12 Jan 2023
59
39th
23,981
21 Nov 2028
65
40th
24,421
04 Feb 2030
66
41st
26,681
13 Apr 2036
73