﻿﻿﻿ Every Day Counts

Centred Square Prime Days

Age: 21,296 days
Date of birth
Your 38th Centred Square Prime Day is on
Tuesday
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
10 Nov 2018
21,313
17
58
19 Jan 2019
21,383
87
58
03 Dec 2019
21,701
405
59
21 Apr 2020
21,841
545
59
18 Dec 2021
22,447
1,151
61
01 Mar 2024
23,251
1,955
63
19 Dec 2038
28,657
7,361
78
04 Dec 2042
30,103
8,807
82
09 May 2062
37,199
15,903
101
15 Apr 2068
39,367
18,071
107
17 Mar 2080
43,721
22,425
119
14 Aug 2093
48,619
27,323
133
10 Dec 2139
65,537
44,241
179
23 Jan 2235
100,279
78,983
274
12 Aug 2258
108,881
87,585
298
15 May 2319
131,071
109,775
358
05 Sep 7777
2,124,679
2,103,383
5817
Ordinal
Day Age
Date
Age
1st
5
09 Jul 1960
0
2nd
13
17 Jul 1960
0
3rd
41
14 Aug 1960
0
4th
61
03 Sep 1960
0
5th
113
25 Oct 1960
0
6th
181
01 Jan 1961
0
7th
313
13 May 1961
0
8th
421
29 Aug 1961
1
9th
613
09 Mar 1962
1
10th
761
04 Aug 1962
2
11th
1,013
13 Apr 1963
2
12th
1,201
18 Oct 1963
3
13th
1,301
26 Jan 1964
3
14th
1,741
10 Apr 1965
4
15th
1,861
08 Aug 1965
5
16th
2,113
17 Apr 1966
5
17th
2,381
10 Jan 1967
6
18th
2,521
30 May 1967
6
19th
3,121
19 Jan 1969
8
20th
3,613
26 May 1970
9
21st
4,513
11 Nov 1972
12
22nd
5,101
22 Jun 1974
13
23rd
7,321
20 Jul 1980
20
24th
8,581
01 Jan 1984
23
25th
9,661
16 Dec 1986
26
26th
9,941
22 Sep 1987
27
27th
10,513
16 Apr 1989
28
28th
12,641
12 Feb 1995
34
29th
13,613
11 Oct 1997
37
30th
14,281
10 Aug 1999
39
31st
14,621
15 Jul 2000
40
32nd
15,313
07 Jun 2002
41
33rd
16,381
10 May 2005
44
34th
19,013
24 Jul 2012
52
35th
19,801
20 Sep 2014
54
36th
20,201
25 Oct 2015
55
37th
21,013
14 Jan 2018
57
38th
21,841
21 Apr 2020
59
1
39th
23,981
01 Mar 2026
65
40th
24,421
15 May 2027
66
41st
26,681
22 Jul 2033
73