21782238 has 16 divisors (see below), whose sum is σ = 43754256. Its totient is φ = 7229120.

The previous prime is 21782237. The next prime is 21782249. The reversal of 21782238 is 83228712.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 21782199 and 21782208.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21782237) 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, 6393 + ... + 9188.

It is an arithmetic number, because the mean of its divisors is an integer number (2734641).

Almost surely, 2^21782238 is an apocalyptic number.

21782238 is an abundant number, since it is smaller than the sum of its proper divisors (21972018).

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

21782238 is a wasteful number, since it uses less digits than its factorization.

21782238 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15819.

The product of its digits is 10752, while the sum is 33.

The square root of 21782238 is about 4667.1445231533. The cubic root of 21782238 is about 279.2763541743.

The spelling of 21782238 in words is "twenty-one million, seven hundred eighty-two thousand, two hundred thirty-eight".