21170155 has 8 divisors (see below), whose sum is σ = 25450992. Its totient is φ = 16904928.

The previous prime is 21170137. The next prime is 21170159. The reversal of 21170155 is 55107112.

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 21170155 - 2¹³ = 21161963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21170159) 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 7 ways as a sum of consecutive naturals, for example, 672 + ... + 6541.

It is an arithmetic number, because the mean of its divisors is an integer number (3181374).

Almost surely, 2^21170155 is an apocalyptic number.

21170155 is a deficient number, since it is larger than the sum of its proper divisors (4280837).

21170155 is an equidigital number, since it uses as much as digits as its factorization.

21170155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7805.

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

The square root of 21170155 is about 4601.1036719465. The cubic root of 21170155 is about 276.6355644784.

Adding to 21170155 its reverse (55107112), we get a palindrome (76277267).

The spelling of 21170155 in words is "twenty-one million, one hundred seventy thousand, one hundred fifty-five".