20421231 has 4 divisors (see below), whose sum is σ = 27228312. Its totient is φ = 13614152.

The previous prime is 20421229. The next prime is 20421241. The reversal of 20421231 is 13212402.

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 20421231 - 2¹ = 20421229 is a prime.

It is a super-2 number, since 2×20421231² = 834053351110722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20421231.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20421241) 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, 3403536 + ... + 3403541.

It is an arithmetic number, because the mean of its divisors is an integer number (6807078).

Almost surely, 2^20421231 is an apocalyptic number.

20421231 is a deficient number, since it is larger than the sum of its proper divisors (6807081).

20421231 is an equidigital number, since it uses as much as digits as its factorization.

20421231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6807080.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 20421231 is about 4518.9856162639. The cubic root of 20421231 is about 273.3341987216.

Adding to 20421231 its reverse (13212402), we get a palindrome (33633633).

The spelling of 20421231 in words is "twenty million, four hundred twenty-one thousand, two hundred thirty-one".