21616165 has 8 divisors (see below), whose sum is σ = 26834040. Its totient is φ = 16696512.

The previous prime is 21616157. The next prime is 21616169. The reversal of 21616165 is 56161612.

It can be written as a sum of positive squares in 4 ways, for example, as 9042049 + 12574116 = 3007^2 + 3546^2 .

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 21616165 - 2³ = 21616157 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21616169) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 74394 + ... + 74683.

It is an arithmetic number, because the mean of its divisors is an integer number (3354255).

Almost surely, 2^21616165 is an apocalyptic number.

It is an amenable number.

21616165 is a deficient number, since it is larger than the sum of its proper divisors (5217875).

21616165 is a wasteful number, since it uses less digits than its factorization.

21616165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 149111.

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

The square root of 21616165 is about 4649.3187673034. The cubic root of 21616165 is about 278.5647861038.

Adding to 21616165 its reverse (56161612), we get a palindrome (77777777).

The spelling of 21616165 in words is "twenty-one million, six hundred sixteen thousand, one hundred sixty-five".