1221355520 has 192 divisors, whose sum is σ = 3656016000. Its totient is φ = 380436480.

The previous prime is 1221355517. The next prime is 1221355543. The reversal of 1221355520 is 255531221.

It is a self number, because there is not a number n which added to its sum of digits gives 1221355520.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 787706 + ... + 789254.

It is an arithmetic number, because the mean of its divisors is an integer number (19041750).

Almost surely, 2^1221355520 is an apocalyptic number.

1221355520 is a gapful number since it is divisible by the number (10) 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 1221355520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1828008000).

1221355520 is an abundant number, since it is smaller than the sum of its proper divisors (2434660480).

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

1221355520 is a wasteful number, since it uses less digits than its factorization.

1221355520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1594 (or 1574 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 26.

The square root of 1221355520 is about 34947.8972185738. The cubic root of 1221355520 is about 1068.9253250438.

Adding to 1221355520 its reverse (255531221), we get a palindrome (1476886741).

The spelling of 1221355520 in words is "one billion, two hundred twenty-one million, three hundred fifty-five thousand, five hundred twenty".