21778416 has 80 divisors (see below), whose sum is σ = 68209920. Its totient is φ = 6598080.

The previous prime is 21778409. The next prime is 21778433. The reversal of 21778416 is 61487712.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2461 + ... + 7043.

It is an arithmetic number, because the mean of its divisors is an integer number (852624).

Almost surely, 2^21778416 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21778416, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34104960).

21778416 is an abundant number, since it is smaller than the sum of its proper divisors (46431504).

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

21778416 is a wasteful number, since it uses less digits than its factorization.

21778416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4611 (or 4599 counting only the distinct ones).

The product of its digits is 18816, while the sum is 36.

The square root of 21778416 is about 4666.7350471181. The cubic root of 21778416 is about 279.2600188975.

The spelling of 21778416 in words is "twenty-one million, seven hundred seventy-eight thousand, four hundred sixteen".