21908842 has 16 divisors (see below), whose sum is σ = 33799752. Its totient is φ = 10644480.

The previous prime is 21908839. The next prime is 21908849. The reversal of 21908842 is 24880912.

It can be written as a sum of positive squares in 4 ways, for example, as 13329801 + 8579041 = 3651^2 + 2929^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21908798 and 21908807.

It is not an unprimeable number, because it can be changed into a prime (21908849) 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 7 ways as a sum of consecutive naturals, for example, 32218 + ... + 32890.

Almost surely, 2^21908842 is an apocalyptic number.

21908842 is a deficient number, since it is larger than the sum of its proper divisors (11890910).

21908842 is a wasteful number, since it uses less digits than its factorization.

21908842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1113.

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 21908842 is about 4680.6881972633. The cubic root of 21908842 is about 279.8163847192.

The spelling of 21908842 in words is "twenty-one million, nine hundred eight thousand, eight hundred forty-two".