21689718 has 8 divisors (see below), whose sum is σ = 43379448. Its totient is φ = 7229904.

The previous prime is 21689693. The next prime is 21689741. The reversal of 21689718 is 81798612.

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

21689718 is an admirable number.

It is a self number, because there is not a number n which added to its sum of digits gives 21689718.

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, 1807471 + ... + 1807482.

It is an arithmetic number, because the mean of its divisors is an integer number (5422431).

Almost surely, 2^21689718 is an apocalyptic number.

21689718 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.

21689718 is a wasteful number, since it uses less digits than its factorization.

21689718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3614958.

The product of its digits is 48384, while the sum is 42.

The square root of 21689718 is about 4657.2221334182. Note that the first 3 decimals coincide. The cubic root of 21689718 is about 278.8803844847.

The spelling of 21689718 in words is "twenty-one million, six hundred eighty-nine thousand, seven hundred eighteen".