21778128 has 30 divisors (see below), whose sum is σ = 60948914. Its totient is φ = 7259328.

The previous prime is 21778117. The next prime is 21778157. The reversal of 21778128 is 82187712.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 18045504 + 3732624 = 4248^2 + 1932^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21778092 and 21778101.

It is a congruent number.

It is an unprimeable number.

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 in 5 ways as a sum of consecutive naturals, for example, 75475 + ... + 75762.

Almost surely, 2^21778128 is an apocalyptic number.

It is an amenable number.

21778128 is an abundant number, since it is smaller than the sum of its proper divisors (39170786).

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

21778128 is a wasteful number, since it uses less digits than its factorization.

21778128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151251 (or 151242 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21778128 is about 4666.7041903253. The cubic root of 21778128 is about 279.2587879044.

The spelling of 21778128 in words is "twenty-one million, seven hundred seventy-eight thousand, one hundred twenty-eight".