Every Day Counts
Centred Square Prime Days
 
Age: 21,022 days
Date of birth
Your 38th Centred Square Prime Day is on
Sunday
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:

Remind me, please


Next Prime Events
Day Age
Event
Days Ahead
Year Age
22 Oct 2018
21,023
tomorrow
57
17 Oct 2019
21,383
361
58
30 Aug 2020
21,701
679
59
17 Jan 2021
21,841
819
59
15 Sep 2022
22,447
1,425
61
27 Nov 2024
23,251
2,229
63
16 Sep 2039
28,657
7,635
78
01 Sep 2043
30,103
9,081
82
04 Feb 2063
37,199
16,177
101
11 Jan 2069
39,367
18,345
107
13 Dec 2080
43,721
22,699
119
12 May 2094
48,619
27,597
133
06 Sep 2140
65,537
44,515
179
21 Oct 2235
100,279
79,257
274
10 May 2259
108,881
87,859
298
10 Feb 2320
131,071
110,049
358
03 Jun 7778
2,124,679
2,103,657
5817
Ordinal
Day Age
Date
Age
1st
5
06 Apr 1961
0
2nd
13
14 Apr 1961
0
3rd
41
12 May 1961
0
4th
61
01 Jun 1961
0
5th
113
23 Jul 1961
0
6th
181
29 Sep 1961
0
7th
313
08 Feb 1962
0
8th
421
27 May 1962
1
9th
613
05 Dec 1962
1
10th
761
02 May 1963
2
11th
1,013
09 Jan 1964
2
12th
1,201
15 Jul 1964
3
13th
1,301
23 Oct 1964
3
14th
1,741
06 Jan 1966
4
15th
1,861
06 May 1966
5
16th
2,113
13 Jan 1967
5
17th
2,381
08 Oct 1967
6
18th
2,521
25 Feb 1968
6
19th
3,121
17 Oct 1969
8
20th
3,613
21 Feb 1971
9
21st
4,513
09 Aug 1973
12
22nd
5,101
20 Mar 1975
13
23rd
7,321
17 Apr 1981
20
24th
8,581
28 Sep 1984
23
25th
9,661
13 Sep 1987
26
26th
9,941
19 Jun 1988
27
27th
10,513
12 Jan 1990
28
28th
12,641
10 Nov 1995
34
29th
13,613
09 Jul 1998
37
30th
14,281
07 May 2000
39
31st
14,621
12 Apr 2001
40
32nd
15,313
05 Mar 2003
41
33rd
16,381
05 Feb 2006
44
34th
19,013
21 Apr 2013
52
35th
19,801
18 Jun 2015
54
36th
20,201
22 Jul 2016
55
37th
21,013
12 Oct 2018
57
38th
21,841
17 Jan 2021
59
1
39th
23,981
27 Nov 2026
65
40th
24,421
10 Feb 2028
66
41st
26,681
19 Apr 2034
73