21744778 has 16 divisors (see below), whose sum is σ = 37455840. Its totient is φ = 9363600.

The previous prime is 21744763. The next prime is 21744803. The reversal of 21744778 is 87744712.

It is a self number, because there is not a number n which added to its sum of digits gives 21744778.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 25593 + ... + 26428.

It is an arithmetic number, because the mean of its divisors is an integer number (2340990).

Almost surely, 2^21744778 is an apocalyptic number.

21744778 is a deficient number, since it is larger than the sum of its proper divisors (15711062).

21744778 is a wasteful number, since it uses less digits than its factorization.

21744778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52053.

The product of its digits is 87808, while the sum is 40.

The square root of 21744778 is about 4663.1296357704. The cubic root of 21744778 is about 279.1161671582.

It can be divided in two parts, 21744 and 778, that added together give a palindrome (22522).

The spelling of 21744778 in words is "twenty-one million, seven hundred forty-four thousand, seven hundred seventy-eight".