21909786 has 16 divisors (see below), whose sum is σ = 44166144. Its totient is φ = 7245504.

The previous prime is 21909743. The next prime is 21909799. The reversal of 21909786 is 68790912.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13615 + ... + 15138.

It is an arithmetic number, because the mean of its divisors is an integer number (2760384).

Almost surely, 2^21909786 is an apocalyptic number.

21909786 is an abundant number, since it is smaller than the sum of its proper divisors (22256358).

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

21909786 is a wasteful number, since it uses less digits than its factorization.

21909786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28885.

The product of its (nonzero) digits is 54432, while the sum is 42.

The square root of 21909786 is about 4680.7890360494. The cubic root of 21909786 is about 279.8204035361.

The spelling of 21909786 in words is "twenty-one million, nine hundred nine thousand, seven hundred eighty-six".