20321531 has 4 divisors (see below), whose sum is σ = 20753952. Its totient is φ = 19889112.

The previous prime is 20321447. The next prime is 20321537. The reversal of 20321531 is 13512302.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20321531 - 2¹⁰ = 20320507 is a prime.

It is a super-2 number, since 2×20321531² = 825929244367922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20321537) 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, 216140 + ... + 216233.

It is an arithmetic number, because the mean of its divisors is an integer number (5188488).

Almost surely, 2^20321531 is an apocalyptic number.

20321531 is a deficient number, since it is larger than the sum of its proper divisors (432421).

20321531 is an equidigital number, since it uses as much as digits as its factorization.

20321531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 432420.

The product of its (nonzero) digits is 180, while the sum is 17.

The square root of 20321531 is about 4507.9408824873. The cubic root of 20321531 is about 272.8886511602. Note that the first 3 decimals are identical.

Adding to 20321531 its reverse (13512302), we get a palindrome (33833833).

The spelling of 20321531 in words is "twenty million, three hundred twenty-one thousand, five hundred thirty-one".