155135221 has 2 divisors, whose sum is σ = 155135222. Its totient is φ = 155135220.

The previous prime is 155135179. The next prime is 155135237. The reversal of 155135221 is 122531551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 152794321 + 2340900 = 12361^2 + 1530^2 .

It is a cyclic number.

It is not a de Polignac number, because 155135221 - 2⁷ = 155135093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155135521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77567610 + 77567611.

It is an arithmetic number, because the mean of its divisors is an integer number (77567611).

Almost surely, 2^155135221 is an apocalyptic number.

It is an amenable number.

155135221 is a deficient number, since it is larger than the sum of its proper divisors (1).

155135221 is an equidigital number, since it uses as much as digits as its factorization.

155135221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1500, while the sum is 25.

The square root of 155135221 is about 12455.3290201423. The cubic root of 155135221 is about 537.3246975466.

Adding to 155135221 its reverse (122531551), we get a palindrome (277666772).

The spelling of 155135221 in words is "one hundred fifty-five million, one hundred thirty-five thousand, two hundred twenty-one".