21778844 has 12 divisors (see below), whose sum is σ = 38157168. Its totient is φ = 10876800.

The previous prime is 21778843. The next prime is 21778859. The reversal of 21778844 is 44887712.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21778843) 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 in 3 ways as a sum of consecutive naturals, for example, 1484 + ... + 6764.

It is an arithmetic number, because the mean of its divisors is an integer number (3179764).

Almost surely, 2^21778844 is an apocalyptic number.

It is an amenable number.

21778844 is a deficient number, since it is larger than the sum of its proper divisors (16378324).

21778844 is a wasteful number, since it uses less digits than its factorization.

21778844 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6316 (or 6314 counting only the distinct ones).

The product of its digits is 100352, while the sum is 41.

The square root of 21778844 is about 4666.7809033637. The cubic root of 21778844 is about 279.2618482700.

It can be divided in two parts, 21778 and 844, that added together give a palindrome (22622).

The spelling of 21778844 in words is "twenty-one million, seven hundred seventy-eight thousand, eight hundred forty-four".