21978433 has 16 divisors (see below), whose sum is σ = 24354000. Its totient is φ = 19740672.

The previous prime is 21978403. The next prime is 21978487. The reversal of 21978433 is 33487912.

It can be written as a sum of positive squares in 8 ways, for example, as 5143824 + 16834609 = 2268^2 + 4103^2 .

It is not a de Polignac number, because 21978433 - 2⁵ = 21978401 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21978392 and 21978401.

It is not an unprimeable number, because it can be changed into a prime (21978403) by changing a digit.

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, 53533 + ... + 53941.

It is an arithmetic number, because the mean of its divisors is an integer number (1522125).

Almost surely, 2^21978433 is an apocalyptic number.

It is an amenable number.

21978433 is a deficient number, since it is larger than the sum of its proper divisors (2375567).

21978433 is a wasteful number, since it uses less digits than its factorization.

21978433 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 564.

The product of its digits is 36288, while the sum is 37.

The square root of 21978433 is about 4688.1161461721. The cubic root of 21978433 is about 280.1123401255.

The spelling of 21978433 in words is "twenty-one million, nine hundred seventy-eight thousand, four hundred thirty-three".