21777828 has 12 divisors (see below), whose sum is σ = 50814960. Its totient is φ = 7259272.

The previous prime is 21777827. The next prime is 21777839. The reversal of 21777828 is 82877712.

It is a tau number, because it is divible by the number of its divisors (12).

It is a self number, because there is not a number n which added to its sum of digits gives 21777828.

It is not an unprimeable number, because it can be changed into a prime (21777827) 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, 907398 + ... + 907421.

It is an arithmetic number, because the mean of its divisors is an integer number (4234580).

Almost surely, 2^21777828 is an apocalyptic number.

It is an amenable number.

21777828 is an abundant number, since it is smaller than the sum of its proper divisors (29037132).

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

21777828 is a wasteful number, since it uses less digits than its factorization.

21777828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1814826 (or 1814824 counting only the distinct ones).

The product of its digits is 87808, while the sum is 42.

The square root of 21777828 is about 4666.6720476159. The cubic root of 21777828 is about 279.2575056083.

The spelling of 21777828 in words is "twenty-one million, seven hundred seventy-seven thousand, eight hundred twenty-eight".