21681338 has 16 divisors (see below), whose sum is σ = 38367744. Its totient is φ = 8992080.

The previous prime is 21681311. The next prime is 21681347. The reversal of 21681338 is 83318612.

It is a happy number.

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 7 ways as a sum of consecutive naturals, for example, 24545 + ... + 25412.

It is an arithmetic number, because the mean of its divisors is an integer number (2397984).

Almost surely, 2^21681338 is an apocalyptic number.

21681338 is a deficient number, since it is larger than the sum of its proper divisors (16686406).

21681338 is a wasteful number, since it uses less digits than its factorization.

21681338 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49997.

The product of its digits is 6912, while the sum is 32.

The square root of 21681338 is about 4656.3223685651. The cubic root of 21681338 is about 278.8444639522.

The spelling of 21681338 in words is "twenty-one million, six hundred eighty-one thousand, three hundred thirty-eight".