155311221 has 16 divisors (see below), whose sum is σ = 224774144. Its totient is φ = 94820544.

The previous prime is 155311217. The next prime is 155311241. The reversal of 155311221 is 122113551.

155311221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 155311221 - 2² = 155311217 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 (155311241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10726 + ... + 20631.

It is an arithmetic number, because the mean of its divisors is an integer number (14048384).

Almost surely, 2^155311221 is an apocalyptic number.

It is an amenable number.

155311221 is a deficient number, since it is larger than the sum of its proper divisors (69462923).

155311221 is a wasteful number, since it uses less digits than its factorization.

155311221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31500.

The product of its digits is 300, while the sum is 21.

The square root of 155311221 is about 12462.3922663347. The cubic root of 155311221 is about 537.5278179942.

Adding to 155311221 its reverse (122113551), we get a palindrome (277424772).

The spelling of 155311221 in words is "one hundred fifty-five million, three hundred eleven thousand, two hundred twenty-one".