21217616 has 40 divisors (see below), whose sum is σ = 47199360. Its totient is φ = 9051264.

The previous prime is 21217597. The next prime is 21217621. The reversal of 21217616 is 61671212.

It is a zygodrome in base 4.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43325 + ... + 43811.

It is an arithmetic number, because the mean of its divisors is an integer number (1179984).

Almost surely, 2^21217616 is an apocalyptic number.

It is an amenable number.

21217616 is an abundant number, since it is smaller than the sum of its proper divisors (25981744).

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

21217616 is a wasteful number, since it uses less digits than its factorization.

21217616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 891 (or 885 counting only the distinct ones).

The product of its digits is 1008, while the sum is 26.

The square root of 21217616 is about 4606.2583514171. The cubic root of 21217616 is about 276.8421383274.

Adding to 21217616 its reverse (61671212), we get a palindrome (82888828).

The spelling of 21217616 in words is "twenty-one million, two hundred seventeen thousand, six hundred sixteen".