1221329556 has 96 divisors (see below), whose sum is σ = 3256041600. Its totient is φ = 395746560.

The previous prime is 1221329507. The next prime is 1221329561. The reversal of 1221329556 is 6559231221.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 1221329556.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 585291 + ... + 587373.

It is an arithmetic number, because the mean of its divisors is an integer number (33917100).

Almost surely, 2^1221329556 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221329556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1628020800).

1221329556 is an abundant number, since it is smaller than the sum of its proper divisors (2034712044).

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

1221329556 is a wasteful number, since it uses less digits than its factorization.

1221329556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2246 (or 2238 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 1221329556 is about 34947.5257493288. The cubic root of 1221329556 is about 1068.9177504615.

The spelling of 1221329556 in words is "one billion, two hundred twenty-one million, three hundred twenty-nine thousand, five hundred fifty-six".