20532781 has 4 divisors (see below), whose sum is σ = 20544700. Its totient is φ = 20520864.

The previous prime is 20532769. The next prime is 20532791. The reversal of 20532781 is 18723502.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 18404100 + 2128681 = 4290^2 + 1459^2 .

It is a cyclic number.

It is not a de Polignac number, because 20532781 - 2⁹ = 20532269 is a prime.

It is a super-2 number, since 2×20532781² = 843190191187922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20532731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2826 + ... + 7003.

It is an arithmetic number, because the mean of its divisors is an integer number (5136175).

Almost surely, 2^20532781 is an apocalyptic number.

It is an amenable number.

20532781 is a deficient number, since it is larger than the sum of its proper divisors (11919).

20532781 is an equidigital number, since it uses as much as digits as its factorization.

20532781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11918.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 20532781 is about 4531.3111788973. The cubic root of 20532781 is about 273.8309869290.

The spelling of 20532781 in words is "twenty million, five hundred thirty-two thousand, seven hundred eighty-one".