21066668 has 36 divisors (see below), whose sum is σ = 45150840. Its totient is φ = 8551872.

The previous prime is 21066641. The next prime is 21066677. The reversal of 21066668 is 86666012.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 896 + ... + 6552.

It is an arithmetic number, because the mean of its divisors is an integer number (1254190).

Almost surely, 2^21066668 is an apocalyptic number.

21066668 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21066668, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22575420).

21066668 is an abundant number, since it is smaller than the sum of its proper divisors (24084172).

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

21066668 is a wasteful number, since it uses less digits than its factorization.

21066668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5694 (or 5685 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 35.

The square root of 21066668 is about 4589.8440060638. The cubic root of 21066668 is about 276.1840647154.

The spelling of 21066668 in words is "twenty-one million, sixty-six thousand, six hundred sixty-eight".