20538281 has 6 divisors (see below), whose sum is σ = 20685882. Its totient is φ = 20391680.

The previous prime is 20538239. The next prime is 20538283. The reversal of 20538281 is 18283502.

It can be written as a sum of positive squares in only one way, i.e., 20025625 + 512656 = 4475^2 + 716^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20538281 is a prime.

It is a super-2 number, since 2×20538281² = 843641972869922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20538283) 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 5 ways as a sum of consecutive naturals, for example, 31721 + ... + 32361.

It is an arithmetic number, because the mean of its divisors is an integer number (3447647).

Almost surely, 2^20538281 is an apocalyptic number.

It is an amenable number.

20538281 is a deficient number, since it is larger than the sum of its proper divisors (147601).

20538281 is an frugal number, since it uses more digits than its factorization.

20538281 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 999 (or 820 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 20538281 is about 4531.9180266196. The cubic root of 20538281 is about 273.8554345992.

The spelling of 20538281 in words is "twenty million, five hundred thirty-eight thousand, two hundred eighty-one".