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21512 = 232689

21512 has 8 divisors (see below), whose sum is σ = 40350. Its totient is φ = 10752.

The previous prime is 21503. The next prime is 21517.

21512 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in only one way, i.e., 21316 + 196 = 146^2 + 14^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×215122 = 925532288, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21493 and 21502.

It is not an unprimeable number, because it can be changed into a prime (21517) by changing a digit.

21512 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1337 + ... + 1352.

221512 is an apocalyptic number.

It is an amenable number.

21512 is a deficient number, since it is larger than the sum of its proper divisors (18838).

21512 is a wasteful number, since it uses less digits than its factorization.

21512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2695 (or 2691 counting only the distinct ones).

The product of its digits is 20, while the sum is 11.

The square root of 21512 is about 146.6696969384. The cubic root of 21512 is about 27.8116611707.

Multiplying 21512 by its sum of digits (11), we get a palindrome (236632).

The spelling of 21512 in words is "twenty-one thousand, five hundred twelve".

Divisors: 1 2 4 8 2689 5378 10756 21512