155535221 has 2 divisors, whose sum is σ = 155535222. Its totient is φ = 155535220.

The previous prime is 155535217. The next prime is 155535239. The reversal of 155535221 is 122535551.

155535221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 151634596 + 3900625 = 12314^2 + 1975^2 .

It is an emirp because it is prime and its reverse (122535551) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 155535221 - 2² = 155535217 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155535251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77767610 + 77767611.

It is an arithmetic number, because the mean of its divisors is an integer number (77767611).

Almost surely, 2^155535221 is an apocalyptic number.

It is an amenable number.

155535221 is a deficient number, since it is larger than the sum of its proper divisors (1).

155535221 is an equidigital number, since it uses as much as digits as its factorization.

155535221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7500, while the sum is 29.

The square root of 155535221 is about 12471.3760668180. The cubic root of 155535221 is about 537.7861131148.

The spelling of 155535221 in words is "one hundred fifty-five million, five hundred thirty-five thousand, two hundred twenty-one".