21138165 has 80 divisors (see below), whose sum is σ = 41469120. Its totient is φ = 10264320.

The previous prime is 21138163. The next prime is 21138179. The reversal of 21138165 is 56183112.

It is not a de Polignac number, because 21138165 - 2¹ = 21138163 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

21138165 is a Rhonda number in base 10.

Its product of digits (1440) is a multiple of the sum of its prime factors (144).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21138163) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 315462 + ... + 315528.

It is an arithmetic number, because the mean of its divisors is an integer number (518364).

Almost surely, 2^21138165 is an apocalyptic number.

It is an amenable number.

21138165 is a deficient number, since it is larger than the sum of its proper divisors (20330955).

21138165 is a wasteful number, since it uses less digits than its factorization.

21138165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 135 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 21138165 is about 4597.6260178488. The cubic root of 21138165 is about 276.4961538639.

The spelling of 21138165 in words is "twenty-one million, one hundred thirty-eight thousand, one hundred sixty-five".