Brain-Teaser 21

From The Sunday Times, 13th August 1961 [link]

Across:

1a. Square of a multiple of 11.
5a. A fourth power.
8a. A multiple of 2d.
9a. A cube reversed.
11a. If added to 4d it gives a square.
12a. 3 times a prime number.
14a. A multiple of 11.
16a. A prime number.
17a. A cube, which is also the sum of three cubes.
18a. An even number.
20a. A multiple of 12.
21a. A prime number.
22a. The square of a palindromic number.

Down:

1d. The product of two consecutive numbers (neither a prime).
2d. See 8a.
3d. A cube.
4d. See 11a.
6d. The sum of the digits of 3d.
7d. The square of (6d reversed).
10d. The product of two consecutive odd numbers.
13d. The product of two consecutive even numbers.
15d. A cube.
16d. A square.
19d. An even multiple of (18a21a).

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