1155521221 has 2 divisors, whose sum is σ = 1155521222. Its totient is φ = 1155521220.

The previous prime is 1155521209. The next prime is 1155521239. The reversal of 1155521221 is 1221255511.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 941630596 + 213890625 = 30686^2 + 14625^2 .

It is a cyclic number.

It is not a de Polignac number, because 1155521221 - 2⁵ = 1155521189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1155521281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 577760610 + 577760611.

It is an arithmetic number, because the mean of its divisors is an integer number (577760611).

Almost surely, 2^1155521221 is an apocalyptic number.

It is an amenable number.

1155521221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1155521221 is an equidigital number, since it uses as much as digits as its factorization.

1155521221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1000, while the sum is 25.

The square root of 1155521221 is about 33992.9584031752. The cubic root of 1155521221 is about 1049.3635511099.

Adding to 1155521221 its reverse (1221255511), we get a palindrome (2376776732).

The spelling of 1155521221 in words is "one billion, one hundred fifty-five million, five hundred twenty-one thousand, two hundred twenty-one".