21685606 has 4 divisors (see below), whose sum is σ = 32528412. Its totient is φ = 10842802.

The previous prime is 21685603. The next prime is 21685607. The reversal of 21685606 is 60658612.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21685603) 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 as a sum of consecutive naturals, namely, 5421400 + ... + 5421403.

It is an arithmetic number, because the mean of its divisors is an integer number (8132103).

Almost surely, 2^21685606 is an apocalyptic number.

21685606 is a deficient number, since it is larger than the sum of its proper divisors (10842806).

21685606 is a wasteful number, since it uses less digits than its factorization.

21685606 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10842805.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 21685606 is about 4656.7806476148. The cubic root of 21685606 is about 278.8627597186.

The spelling of 21685606 in words is "twenty-one million, six hundred eighty-five thousand, six hundred six".