20131231 has 4 divisors (see below), whose sum is σ = 20276200. Its totient is φ = 19986264.

The previous prime is 20131229. The next prime is 20131259. The reversal of 20131231 is 13213102.

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 20131231 - 2¹ = 20131229 is a prime.

It is a super-2 number, since 2×20131231² = 810532923150722, 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 (20131211) 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, 72276 + ... + 72553.

It is an arithmetic number, because the mean of its divisors is an integer number (5069050).

Almost surely, 2^20131231 is an apocalyptic number.

20131231 is a deficient number, since it is larger than the sum of its proper divisors (144969).

20131231 is a wasteful number, since it uses less digits than its factorization.

20131231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144968.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 20131231 is about 4486.7840375931. The cubic root of 20131231 is about 272.0341607542.

Adding to 20131231 its reverse (13213102), we get a palindrome (33344333).

The spelling of 20131231 in words is "twenty million, one hundred thirty-one thousand, two hundred thirty-one".