21685289 has 8 divisors (see below), whose sum is σ = 22889280. Its totient is φ = 20487600.

The previous prime is 21685277. The next prime is 21685309. The reversal of 21685289 is 98258612.

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 21685289 - 2¹² = 21681193 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21685249) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6644 + ... + 9354.

It is an arithmetic number, because the mean of its divisors is an integer number (2861160).

Almost surely, 2^21685289 is an apocalyptic number.

It is an amenable number.

21685289 is a deficient number, since it is larger than the sum of its proper divisors (1203991).

21685289 is a wasteful number, since it uses less digits than its factorization.

21685289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3151.

The product of its digits is 69120, while the sum is 41.

The square root of 21685289 is about 4656.7466111009. The cubic root of 21685289 is about 278.8614009076.

The spelling of 21685289 in words is "twenty-one million, six hundred eighty-five thousand, two hundred eighty-nine".