1221987179556 has 960 divisors, whose sum is σ = 4107304599552. Its totient is φ = 311351040000.

The previous prime is 1221987179531. The next prime is 1221987179639. The reversal of 1221987179556 is 6559717891221.

1221987179556 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 9 + 8 + 7 + 1 + 79 + 556 = 666.

Its product of digits (19051200) is a multiple of the sum of its prime divisors (675).

It is a junction number, because it is equal to n+sod(n) for n = 1221987179493 and 1221987179502.

It is an unprimeable number.

It is a polite number, since it can be written in 319 ways as a sum of consecutive naturals, for example, 2345464576 + ... + 2345465096.

Almost surely, 2^{1221987179556} 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 1221987179556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2053652299776).

1221987179556 is an abundant number, since it is smaller than the sum of its proper divisors (2885317419996).

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

1221987179556 is a wasteful number, since it uses less digits than its factorization.

1221987179556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 686 (or 675 counting only the distinct ones).

The product of its digits is 19051200, while the sum is 63.

The spelling of 1221987179556 in words is "one trillion, two hundred twenty-one billion, nine hundred eighty-seven million, one hundred seventy-nine thousand, five hundred fifty-six".