1221312220 has 24 divisors (see below), whose sum is σ = 2566612944. Its totient is φ = 488171136.

The previous prime is 1221312217. The next prime is 1221312269. The reversal of 1221312220 is 222131221.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 1221312194 and 1221312203.

It is a congruent number.

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, 7144 + ... + 49936.

It is an arithmetic number, because the mean of its divisors is an integer number (106942206).

Almost surely, 2^1221312220 is an apocalyptic number.

1221312220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221312220 is an abundant number, since it is smaller than the sum of its proper divisors (1345300724).

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

1221312220 is a wasteful number, since it uses less digits than its factorization.

1221312220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44229 (or 44227 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 1221312220 is about 34947.2777194448. The cubic root of 1221312220 is about 1068.9126929006.

Adding to 1221312220 its reverse (222131221), we get a palindrome (1443443441).

The spelling of 1221312220 in words is "one billion, two hundred twenty-one million, three hundred twelve thousand, two hundred twenty".