155170021 has 4 divisors (see below), whose sum is σ = 155207052. Its totient is φ = 155132992.

The previous prime is 155170013. The next prime is 155170049. The reversal of 155170021 is 120071551.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 120071551 = 9133 ⋅13147.

It can be written as a sum of positive squares in 2 ways, for example, as 81450625 + 73719396 = 9025^2 + 8586^2 .

It is a cyclic number.

It is not a de Polignac number, because 155170021 - 2³ = 155170013 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 155169974 and 155170001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155170921) 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 3 ways as a sum of consecutive naturals, for example, 11290 + ... + 20923.

It is an arithmetic number, because the mean of its divisors is an integer number (38801763).

Almost surely, 2^155170021 is an apocalyptic number.

It is an amenable number.

155170021 is a deficient number, since it is larger than the sum of its proper divisors (37031).

155170021 is an equidigital number, since it uses as much as digits as its factorization.

155170021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37030.

The product of its (nonzero) digits is 350, while the sum is 22.

The square root of 155170021 is about 12456.7259342092. The cubic root of 155170021 is about 537.3648721791.

The spelling of 155170021 in words is "one hundred fifty-five million, one hundred seventy thousand, twenty-one".