21166165 has 16 divisors (see below), whose sum is σ = 26040960. Its totient is φ = 16511040.

The previous prime is 21166163. The next prime is 21166177. The reversal of 21166165 is 56166112.

It is not a de Polignac number, because 21166165 - 2¹ = 21166163 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166163) 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, 38422 + ... + 38968.

It is an arithmetic number, because the mean of its divisors is an integer number (1627560).

Almost surely, 2^21166165 is an apocalyptic number.

It is an amenable number.

21166165 is a deficient number, since it is larger than the sum of its proper divisors (4874795).

21166165 is a wasteful number, since it uses less digits than its factorization.

21166165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 732.

The product of its digits is 2160, while the sum is 28.

The square root of 21166165 is about 4600.6700598934. The cubic root of 21166165 is about 276.6181839530.

It can be divided in two parts, 2116 and 6165, that added together give a square (8281 = 91²).

The spelling of 21166165 in words is "twenty-one million, one hundred sixty-six thousand, one hundred sixty-five".