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21016 has 16 divisors (see below), whose sum is σ = 41040. Its totient is φ = 10080.

The previous prime is 21013. The next prime is 21017. The reversal of 21016 is 61012.

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

It is a junction number, because it is equal to n+sod(n) for n = 20993 and 21011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 261 + ... + 331.

It is an arithmetic number, because the mean of its divisors is an integer number (2565).

221016 is an apocalyptic number.

It is an amenable number.

21016 is a deficient number, since it is larger than the sum of its proper divisors (20024).

21016 is a wasteful number, since it uses less digits than its factorization.

21016 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 114 (or 110 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21016 is about 144.9689621954. The cubic root of 21016 is about 27.5962467766.

Adding to 21016 its reverse (61012), we get a palindrome (82028).

The spelling of 21016 in words is "twenty-one thousand, sixteen".