20181331 has 4 divisors (see below), whose sum is σ = 20191000. Its totient is φ = 20171664.

The previous prime is 20181323. The next prime is 20181347. The reversal of 20181331 is 13318102.

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 is a cyclic number.

It is not a de Polignac number, because 20181331 - 2³ = 20181323 is a prime.

It is a super-2 number, since 2×20181331² = 814572241863122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20181299 and 20181308.

It is not an unprimeable number, because it can be changed into a prime (20181311) 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, 261 + ... + 6358.

It is an arithmetic number, because the mean of its divisors is an integer number (5047750).

Almost surely, 2^20181331 is an apocalyptic number.

20181331 is a deficient number, since it is larger than the sum of its proper divisors (9669).

20181331 is an equidigital number, since it uses as much as digits as its factorization.

20181331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9668.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 20181331 is about 4492.3636317645. The cubic root of 20181331 is about 272.2596416021.

Adding to 20181331 its reverse (13318102), we get a palindrome (33499433).

The spelling of 20181331 in words is "twenty million, one hundred eighty-one thousand, three hundred thirty-one".