1221645276 has 72 divisors (see below), whose sum is σ = 3229218720. Its totient is φ = 388675584.

The previous prime is 1221645259. The next prime is 1221645281. The reversal of 1221645276 is 6725461221.

It is a happy number.

1221645276 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 645 + 2 + 7 + 6 = 666.

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 1221645276.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 469836 + ... + 472428.

It is an arithmetic number, because the mean of its divisors is an integer number (44850260).

Almost surely, 2^1221645276 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 1221645276, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1614609360).

1221645276 is an abundant number, since it is smaller than the sum of its proper divisors (2007573444).

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

1221645276 is a wasteful number, since it uses less digits than its factorization.

1221645276 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3195 (or 3190 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 1221645276 is about 34952.0425154239. The cubic root of 1221645276 is about 1069.0098494462.

The spelling of 1221645276 in words is "one billion, two hundred twenty-one million, six hundred forty-five thousand, two hundred seventy-six".