21778443 has 8 divisors (see below), whose sum is σ = 32264400. Its totient is φ = 14518944.

The previous prime is 21778441. The next prime is 21778457. The reversal of 21778443 is 34487712.

It is a happy number.

It is not a de Polignac number, because 21778443 - 2¹ = 21778441 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21778398 and 21778407.

It is not an unprimeable number, because it can be changed into a prime (21778441) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 403278 + ... + 403331.

It is an arithmetic number, because the mean of its divisors is an integer number (4033050).

Almost surely, 2^21778443 is an apocalyptic number.

21778443 is a deficient number, since it is larger than the sum of its proper divisors (10485957).

21778443 is an equidigital number, since it uses as much as digits as its factorization.

21778443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 806618 (or 806612 counting only the distinct ones).

The product of its digits is 37632, while the sum is 36.

The square root of 21778443 is about 4666.7379399319. The cubic root of 21778443 is about 279.2601343025.

The spelling of 21778443 in words is "twenty-one million, seven hundred seventy-eight thousand, four hundred forty-three".