21616164 has 18 divisors (see below), whose sum is σ = 54640950. Its totient is φ = 7205376.

The previous prime is 21616157. The next prime is 21616169. The reversal of 21616164 is 46161612.

It can be written as a sum of positive squares in only one way, i.e., 19873764 + 1742400 = 4458^2 + 1320^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a nude number because it is divisible by every one of its digits.

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

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 300189 + ... + 300260.

Almost surely, 2^21616164 is an apocalyptic number.

It is an amenable number.

21616164 is an abundant number, since it is smaller than the sum of its proper divisors (33024786).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21616164 is a wasteful number, since it uses less digits than its factorization.

21616164 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 600459 (or 600454 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21616164 is about 4649.3186597608. The cubic root of 21616164 is about 278.5647818082.

Adding to 21616164 its reverse (46161612), we get a palindrome (67777776).

It can be divided in two parts, 216161 and 64, that added together give a square (216225 = 465²).

The spelling of 21616164 in words is "twenty-one million, six hundred sixteen thousand, one hundred sixty-four".