21688063 has 4 divisors (see below), whose sum is σ = 22829560. Its totient is φ = 20546568.

The previous prime is 21688049. The next prime is 21688067. The reversal of 21688063 is 36088612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21688063 - 2¹³ = 21679871 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21688067) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 570720 + ... + 570757.

It is an arithmetic number, because the mean of its divisors is an integer number (5707390).

Almost surely, 2^21688063 is an apocalyptic number.

21688063 is a deficient number, since it is larger than the sum of its proper divisors (1141497).

21688063 is a wasteful number, since it uses less digits than its factorization.

21688063 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1141496.

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 21688063 is about 4657.0444490041. The cubic root of 21688063 is about 278.8732911271.

The spelling of 21688063 in words is "twenty-one million, six hundred eighty-eight thousand, sixty-three".