21689905 has 8 divisors (see below), whose sum is σ = 26056512. Its totient is φ = 17332848.

The previous prime is 21689903. The next prime is 21689917. The reversal of 21689905 is 50998612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21689905 - 2¹ = 21689903 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21689903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4342 + ... + 7888.

It is an arithmetic number, because the mean of its divisors is an integer number (3257064).

Almost surely, 2^21689905 is an apocalyptic number.

It is an amenable number.

21689905 is a deficient number, since it is larger than the sum of its proper divisors (4366607).

21689905 is a wasteful number, since it uses less digits than its factorization.

21689905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4775.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 21689905 is about 4657.2422097203. The cubic root of 21689905 is about 278.8811859471.

The spelling of 21689905 in words is "twenty-one million, six hundred eighty-nine thousand, nine hundred five".