21688106 has 16 divisors (see below), whose sum is σ = 35650368. Its totient is φ = 9813600.

The previous prime is 21688067. The next prime is 21688109. The reversal of 21688106 is 60188612.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21688109) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3011 + ... + 7241.

It is an arithmetic number, because the mean of its divisors is an integer number (2228148).

Almost surely, 2^21688106 is an apocalyptic number.

21688106 is a deficient number, since it is larger than the sum of its proper divisors (13962262).

21688106 is a wasteful number, since it uses less digits than its factorization.

21688106 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4477.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21688106 is about 4657.0490656638. The cubic root of 21688106 is about 278.8734754304.

The spelling of 21688106 in words is "twenty-one million, six hundred eighty-eight thousand, one hundred six".