20021231 has 4 divisors (see below), whose sum is σ = 21075000. Its totient is φ = 18967464.

The previous prime is 20021213. The next prime is 20021233. The reversal of 20021231 is 13212002.

It is a happy number.

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 20021231 - 2¹⁰ = 20020207 is a prime.

It is a super-2 number, since 2×20021231² = 801699381510722, 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 (20021233) 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, 526856 + ... + 526893.

It is an arithmetic number, because the mean of its divisors is an integer number (5268750).

Almost surely, 2^20021231 is an apocalyptic number.

20021231 is a deficient number, since it is larger than the sum of its proper divisors (1053769).

20021231 is a wasteful number, since it uses less digits than its factorization.

20021231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1053768.

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 20021231 is about 4474.5090233455. The cubic root of 20021231 is about 271.5377773597.

Adding to 20021231 its reverse (13212002), we get a palindrome (33233233).

The spelling of 20021231 in words is "twenty million, twenty-one thousand, two hundred thirty-one".