155505221 has 8 divisors (see below), whose sum is σ = 161080920. Its totient is φ = 149943808.

The previous prime is 155505197. The next prime is 155505241. The reversal of 155505221 is 122505551.

It can be written as a sum of positive squares in 4 ways, for example, as 110481121 + 45024100 = 10511^2 + 6710^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 155505221 - 2¹⁰ = 155504197 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155505241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21725 + ... + 27981.

It is an arithmetic number, because the mean of its divisors is an integer number (20135115).

Almost surely, 2^155505221 is an apocalyptic number.

It is an amenable number.

155505221 is a deficient number, since it is larger than the sum of its proper divisors (5575699).

155505221 is an equidigital number, since it uses as much as digits as its factorization.

155505221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7143.

The product of its (nonzero) digits is 2500, while the sum is 26.

The square root of 155505221 is about 12470.1732546104. The cubic root of 155505221 is about 537.7515344071.

The spelling of 155505221 in words is "one hundred fifty-five million, five hundred five thousand, two hundred twenty-one".