1155666221 has 16 divisors (see below), whose sum is σ = 1214051328. Its totient is φ = 1098921600.

The previous prime is 1155666199. The next prime is 1155666223. The reversal of 1155666221 is 1226665511.

It is a cyclic number.

It is not a de Polignac number, because 1155666221 - 2³⁰ = 81924397 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1155666223) 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, 521111 + ... + 523323.

It is an arithmetic number, because the mean of its divisors is an integer number (75878208).

Almost surely, 2^1155666221 is an apocalyptic number.

It is an amenable number.

1155666221 is a deficient number, since it is larger than the sum of its proper divisors (58385107).

1155666221 is a wasteful number, since it uses less digits than its factorization.

1155666221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2572.

The product of its digits is 21600, while the sum is 35.

The square root of 1155666221 is about 33995.0911309265. The cubic root of 1155666221 is about 1049.4074422268.

It can be divided in two parts, 11556 and 66221, that added together give a palindrome (77777).

The spelling of 1155666221 in words is "one billion, one hundred fifty-five million, six hundred sixty-six thousand, two hundred twenty-one".