21688617 has 16 divisors (see below), whose sum is σ = 30818880. Its totient is φ = 13519872.

The previous prime is 21688603. The next prime is 21688619. The reversal of 21688617 is 71688612.

It is not a de Polignac number, because 21688617 - 2¹⁰ = 21687593 is a prime.

It is a super-3 number, since 3×21688617³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21688619) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7009 + ... + 9617.

It is an arithmetic number, because the mean of its divisors is an integer number (1926180).

Almost surely, 2^21688617 is an apocalyptic number.

It is an amenable number.

21688617 is a deficient number, since it is larger than the sum of its proper divisors (9130263).

21688617 is a wasteful number, since it uses less digits than its factorization.

21688617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2792.

The product of its digits is 32256, while the sum is 39.

The square root of 21688617 is about 4657.1039284087. The cubic root of 21688617 is about 278.8756656205.

The spelling of 21688617 in words is "twenty-one million, six hundred eighty-eight thousand, six hundred seventeen".