155315221 has 2 divisors, whose sum is σ = 155315222. Its totient is φ = 155315220.

The previous prime is 155315219. The next prime is 155315227. The reversal of 155315221 is 122513551.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 120670225 + 34644996 = 10985^2 + 5886^2 .

It is a cyclic number.

It is not a de Polignac number, because 155315221 - 2¹ = 155315219 is a prime.

Together with 155315219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155315227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77657610 + 77657611.

It is an arithmetic number, because the mean of its divisors is an integer number (77657611).

Almost surely, 2^155315221 is an apocalyptic number.

It is an amenable number.

155315221 is a deficient number, since it is larger than the sum of its proper divisors (1).

155315221 is an equidigital number, since it uses as much as digits as its factorization.

155315221 is an evil number, because the sum of its binary digits is even.

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

The square root of 155315221 is about 12462.5527481331. The cubic root of 155315221 is about 537.5324325842.

Adding to 155315221 its reverse (122513551), we get a palindrome (277828772).

The spelling of 155315221 in words is "one hundred fifty-five million, three hundred fifteen thousand, two hundred twenty-one".