21778928 has 10 divisors (see below), whose sum is σ = 42196704. Its totient is φ = 10889456.

The previous prime is 21778927. The next prime is 21778931. The reversal of 21778928 is 82987712.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21778927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 680576 + ... + 680607.

Almost surely, 2^21778928 is an apocalyptic number.

It is an amenable number.

21778928 is a deficient number, since it is larger than the sum of its proper divisors (20417776).

21778928 is a wasteful number, since it uses less digits than its factorization.

21778928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1361191 (or 1361185 counting only the distinct ones).

The product of its digits is 112896, while the sum is 44.

The square root of 21778928 is about 4666.7899031347. The cubic root of 21778928 is about 279.2622073029.

The spelling of 21778928 in words is "twenty-one million, seven hundred seventy-eight thousand, nine hundred twenty-eight".