21311616 has 128 divisors (see below), whose sum is σ = 62668800. Its totient is φ = 6386688.

The previous prime is 21311611. The next prime is 21311621. The reversal of 21311616 is 61611312.

21311616 = 345² + 346² + ... + 471².

It is an interprime number because it is at equal distance from previous prime (21311611) and next prime (21311621).

It is a tau number, because it is divible by the number of its divisors (128).

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

It is a junction number, because it is equal to n+sod(n) for n = 21311592 and 21311601.

It is not an unprimeable number, because it can be changed into a prime (21311611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 167745 + ... + 167871.

It is an arithmetic number, because the mean of its divisors is an integer number (489600).

Almost surely, 2^21311616 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21311616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31334400).

21311616 is an abundant number, since it is smaller than the sum of its proper divisors (41357184).

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

21311616 is a wasteful number, since it uses less digits than its factorization.

21311616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186 (or 174 counting only the distinct ones).

The product of its digits is 216, while the sum is 21.

The square root of 21311616 is about 4616.4505845942. The cubic root of 21311616 is about 277.2503655498.

Adding to 21311616 its reverse (61611312), we get a palindrome (82922928).

The spelling of 21311616 in words is "twenty-one million, three hundred eleven thousand, six hundred sixteen".