231221220 has 24 divisors (see below), whose sum is σ = 647419584. Its totient is φ = 61658976.

The previous prime is 231221209. The next prime is 231221239. The reversal of 231221220 is 22122132.

It is a happy number.

231221220 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 231221220.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1926784 + ... + 1926903.

It is an arithmetic number, because the mean of its divisors is an integer number (26975816).

Almost surely, 2^231221220 is an apocalyptic number.

231221220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

231221220 is an abundant number, since it is smaller than the sum of its proper divisors (416198364).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

231221220 is a wasteful number, since it uses less digits than its factorization.

231221220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3853699 (or 3853697 counting only the distinct ones).

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

The square root of 231221220 is about 15205.9600157307. The cubic root of 231221220 is about 613.7750487189.

Adding to 231221220 its reverse (22122132), we get a palindrome (253343352).

It can be divided in two parts, 23122 and 1220, that added together give a palindrome (24342).

The spelling of 231221220 in words is "two hundred thirty-one million, two hundred twenty-one thousand, two hundred twenty".