20513 has 4 divisors (see below), whose sum is σ = 20868. Its totient is φ = 20160.
The previous prime is 20509. The next prime is 20521. The reversal of 20513 is 31502.
20513 is an esthetic number in base 6, because in such base its adjacent digits differ by 1.
It is a semiprime because it is the product of two primes.
It can be written as a sum of positive squares in 2 ways, for example, as 12769 + 7744 = 113^2 + 88^2 .
It is a cyclic number.
It is not a de Polignac number, because 20513 - 22 = 20509 is a prime.
It is a Duffinian number.
It is a plaindrome in base 11.
It is a nialpdrome in base 12.
It is a junction number, because it is equal to n+sod(n) for n = 20494 and 20503.
It is not an unprimeable number, because it can be changed into a prime (20533) by changing a digit.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 68 + ... + 213.
It is an arithmetic number, because the mean of its divisors is an integer number (5217).
220513 is an apocalyptic number.
It is an amenable number.
20513 is a deficient number, since it is larger than the sum of its proper divisors (355).
20513 is an equidigital number, since it uses as much as digits as its factorization.
20513 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 354.
The product of its (nonzero) digits is 30, while the sum is 11.
The square root of 20513 is about 143.2236014070. The cubic root of 20513 is about 27.3743023668.
Subtracting from 20513 its sum of digits (11), we obtain a palindrome (20502).
The spelling of 20513 in words is "twenty thousand, five hundred thirteen".
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