21778843 has 2 divisors, whose sum is σ = 21778844. Its totient is φ = 21778842.

The previous prime is 21778837. The next prime is 21778859. The reversal of 21778843 is 34887712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21778843 - 2⁵ = 21778811 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21778796 and 21778805.

It is not a weakly prime, because it can be changed into another prime (21778873) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10889421 + 10889422.

It is an arithmetic number, because the mean of its divisors is an integer number (10889422).

Almost surely, 2^21778843 is an apocalyptic number.

21778843 is a deficient number, since it is larger than the sum of its proper divisors (1).

21778843 is an equidigital number, since it uses as much as digits as its factorization.

21778843 is an evil number, because the sum of its binary digits is even.

The product of its digits is 75264, while the sum is 40.

The square root of 21778843 is about 4666.7807962235. The cubic root of 21778843 is about 279.2618439958.

The spelling of 21778843 in words is "twenty-one million, seven hundred seventy-eight thousand, eight hundred forty-three".