155506221 has 24 divisors (see below), whose sum is σ = 247054080. Its totient is φ = 93656736.

The previous prime is 155506217. The next prime is 155506237. The reversal of 155506221 is 122605551.

155506221 is a `hidden beast` number, since 155 + 506 + 2 + 2 + 1 = 666.

It is not a de Polignac number, because 155506221 - 2² = 155506217 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155506201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8641 + ... + 19638.

It is an arithmetic number, because the mean of its divisors is an integer number (10293920).

Almost surely, 2^155506221 is an apocalyptic number.

It is an amenable number.

155506221 is a deficient number, since it is larger than the sum of its proper divisors (91547859).

155506221 is a wasteful number, since it uses less digits than its factorization.

155506221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28345 (or 28342 counting only the distinct ones).

The product of its (nonzero) digits is 3000, while the sum is 27.

The square root of 155506221 is about 12470.2133502198. The cubic root of 155506221 is about 537.7526871024.

The spelling of 155506221 in words is "one hundred fifty-five million, five hundred six thousand, two hundred twenty-one".