1221758828720 has 80 divisors (see below), whose sum is σ = 2935017384960. Its totient is φ = 472487904000.

The previous prime is 1221758828699. The next prime is 1221758828723. The reversal of 1221758828720 is 278288571221.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (1221758828723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2372111 + ... + 2840849.

It is an arithmetic number, because the mean of its divisors is an integer number (36687717312).

Almost surely, 2^{1221758828720} is an apocalyptic number.

1221758828720 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 1221758828720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1467508692480).

1221758828720 is an abundant number, since it is smaller than the sum of its proper divisors (1713258556240).

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

1221758828720 is a wasteful number, since it uses less digits than its factorization.

1221758828720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 469834 (or 469828 counting only the distinct ones).

The product of its (nonzero) digits is 2007040, while the sum is 53.

The spelling of 1221758828720 in words is "one trillion, two hundred twenty-one billion, seven hundred fifty-eight million, eight hundred twenty-eight thousand, seven hundred twenty".