21063666 has 64 divisors (see below), whose sum is σ = 48746880. Its totient is φ = 6013440.

The previous prime is 21063569. The next prime is 21063673. The reversal of 21063666 is 66636012.

It is an unprimeable number.

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 in 31 ways as a sum of consecutive naturals, for example, 90286 + ... + 90518.

It is an arithmetic number, because the mean of its divisors is an integer number (761670).

Almost surely, 2^21063666 is an apocalyptic number.

21063666 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21063666, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24373440).

21063666 is an abundant number, since it is smaller than the sum of its proper divisors (27683214).

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

21063666 is a wasteful number, since it uses less digits than its factorization.

21063666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 331.

The product of its (nonzero) digits is 7776, while the sum is 30.

The square root of 21063666 is about 4589.5169680479. The cubic root of 21063666 is about 276.1709453499.

Adding to 21063666 its reverse (66636012), we get a palindrome (87699678).

The spelling of 21063666 in words is "twenty-one million, sixty-three thousand, six hundred sixty-six".