21739165 has 16 divisors (see below), whose sum is σ = 30621312. Its totient is φ = 14503104.

The previous prime is 21739129. The next prime is 21739189. The reversal of 21739165 is 56193712.

It is not a de Polignac number, because 21739165 - 2¹⁹ = 21214877 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21739165.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7099 + ... + 9688.

It is an arithmetic number, because the mean of its divisors is an integer number (1913832).

Almost surely, 2^21739165 is an apocalyptic number.

It is an amenable number.

21739165 is a deficient number, since it is larger than the sum of its proper divisors (8882147).

21739165 is a wasteful number, since it uses less digits than its factorization.

21739165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16836.

The product of its digits is 11340, while the sum is 34.

The square root of 21739165 is about 4662.5277479067. The cubic root of 21739165 is about 279.0921489185.

It can be divided in two parts, 21739 and 165, that added together give a square (21904 = 148²).

The spelling of 21739165 in words is "twenty-one million, seven hundred thirty-nine thousand, one hundred sixty-five".