1155221661 has 16 divisors (see below), whose sum is σ = 1701596160. Its totient is φ = 691270320.

The previous prime is 1155221653. The next prime is 1155221663. The reversal of 1155221661 is 1661225511.

It is not a de Polignac number, because 1155221661 - 2³ = 1155221653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1155221663) 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, 218955 + ... + 224168.

It is an arithmetic number, because the mean of its divisors is an integer number (106349760).

Almost surely, 2^1155221661 is an apocalyptic number.

1155221661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1155221661 is a deficient number, since it is larger than the sum of its proper divisors (546374499).

1155221661 is a wasteful number, since it uses less digits than its factorization.

1155221661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 443216.

The product of its digits is 3600, while the sum is 30.

The square root of 1155221661 is about 33988.5519109008. The cubic root of 1155221661 is about 1049.2728634596.

The spelling of 1155221661 in words is "one billion, one hundred fifty-five million, two hundred twenty-one thousand, six hundred sixty-one".