31123211220 has 144 divisors (see below), whose sum is σ = 97764226560. Its totient is φ = 8004987648.

The previous prime is 31123211167. The next prime is 31123211257. The reversal of 31123211220 is 2211232113.

31123211220 is a `hidden beast` number, since 311 + 2 + 321 + 12 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 31123211193 and 31123211202.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 6193629 + ... + 6198651.

It is an arithmetic number, because the mean of its divisors is an integer number (678918240).

Almost surely, 2^31123211220 is an apocalyptic number.

31123211220 is a gapful number since it is divisible by the number (30) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31123211220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (48882113280).

31123211220 is an abundant number, since it is smaller than the sum of its proper divisors (66641015340).

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

31123211220 is a wasteful number, since it uses less digits than its factorization.

31123211220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6254 (or 6249 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

Adding to 31123211220 its reverse (2211232113), we get a palindrome (33334443333).

The spelling of 31123211220 in words is "thirty-one billion, one hundred twenty-three million, two hundred eleven thousand, two hundred twenty".