1221591168 has 576 divisors, whose sum is σ = 4625618400. Its totient is φ = 306561024.

The previous prime is 1221591143. The next prime is 1221591179. The reversal of 1221591168 is 8611951221.

1221591168 is a `hidden beast` number, since 1 + 2 + 2 + 1 + 591 + 1 + 68 = 666.

It is a tau number, because it is divible by the number of its divisors (576).

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

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 18232671 + ... + 18232737.

Almost surely, 2^1221591168 is an apocalyptic number.

1221591168 is a gapful number since it is divisible by the number (18) 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 1221591168, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2312809200).

1221591168 is an abundant number, since it is smaller than the sum of its proper divisors (3404027232).

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

1221591168 is a wasteful number, since it uses less digits than its factorization.

1221591168 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137 (or 115 counting only the distinct ones).

The product of its digits is 8640, while the sum is 36.

The square root of 1221591168 is about 34951.2684748351. The cubic root of 1221591168 is about 1068.9940666763.

The spelling of 1221591168 in words is "one billion, two hundred twenty-one million, five hundred ninety-one thousand, one hundred sixty-eight".