21838666 has 12 divisors (see below), whose sum is σ = 33066738. Its totient is φ = 10817352.

The previous prime is 21838651. The next prime is 21838669. The reversal of 21838666 is 66683812.

It can be written as a sum of positive squares in only one way, i.e., 11758041 + 10080625 = 3429^2 + 3175^2 .

It is not an unprimeable number, because it can be changed into a prime (21838669) 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 in 5 ways as a sum of consecutive naturals, for example, 31920 + ... + 32596.

Almost surely, 2^21838666 is an apocalyptic number.

21838666 is a deficient number, since it is larger than the sum of its proper divisors (11228072).

21838666 is an equidigital number, since it uses as much as digits as its factorization.

21838666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 933 (or 806 counting only the distinct ones).

The product of its digits is 82944, while the sum is 40.

The square root of 21838666 is about 4673.1858512154. The cubic root of 21838666 is about 279.5173061140.

The spelling of 21838666 in words is "twenty-one million, eight hundred thirty-eight thousand, six hundred sixty-six".