155940221 has 8 divisors (see below), whose sum is σ = 161785080. Its totient is φ = 150126592.

The previous prime is 155940139. The next prime is 155940227. The reversal of 155940221 is 122049551.

It can be written as a sum of positive squares in 4 ways, for example, as 4305625 + 151634596 = 2075^2 + 12314^2 .

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 155940221 - 2¹⁴ = 155923837 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155940227) 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 in 7 ways as a sum of consecutive naturals, for example, 2621 + ... + 17853.

It is an arithmetic number, because the mean of its divisors is an integer number (20223135).

Almost surely, 2^155940221 is an apocalyptic number.

It is an amenable number.

155940221 is a deficient number, since it is larger than the sum of its proper divisors (5844859).

155940221 is a wasteful number, since it uses less digits than its factorization.

155940221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15615.

The product of its (nonzero) digits is 3600, while the sum is 29.

The square root of 155940221 is about 12487.6026922704. The cubic root of 155940221 is about 538.2524910847.

Adding to 155940221 its reverse (122049551), we get a palindrome (277989772).

The spelling of 155940221 in words is "one hundred fifty-five million, nine hundred forty thousand, two hundred twenty-one".