21686766 has 8 divisors (see below), whose sum is σ = 43373544. Its totient is φ = 7228920.

The previous prime is 21686741. The next prime is 21686813. The reversal of 21686766 is 66768612.

It is a happy number.

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

21686766 is an admirable number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1807225 + ... + 1807236.

It is an arithmetic number, because the mean of its divisors is an integer number (5421693).

Almost surely, 2^21686766 is an apocalyptic number.

21686766 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21686766 is a wasteful number, since it uses less digits than its factorization.

21686766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3614466.

The product of its digits is 145152, while the sum is 42.

The square root of 21686766 is about 4656.9051955134. The cubic root of 21686766 is about 278.8677319113.

The spelling of 21686766 in words is "twenty-one million, six hundred eighty-six thousand, seven hundred sixty-six".