21909942 has 12 divisors (see below), whose sum is σ = 47471580. Its totient is φ = 7303308.

The previous prime is 21909941. The next prime is 21909977. The reversal of 21909942 is 24990912.

It is a junction number, because it is equal to n+sod(n) for n = 21909897 and 21909906.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909941) 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 5 ways as a sum of consecutive naturals, for example, 608592 + ... + 608627.

It is an arithmetic number, because the mean of its divisors is an integer number (3955965).

Almost surely, 2^21909942 is an apocalyptic number.

21909942 is an abundant number, since it is smaller than the sum of its proper divisors (25561638).

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

21909942 is a wasteful number, since it uses less digits than its factorization.

21909942 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1217227 (or 1217224 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 21909942 is about 4680.8056998769. The cubic root of 21909942 is about 279.8210676515.

The spelling of 21909942 in words is "twenty-one million, nine hundred nine thousand, nine hundred forty-two".