21786906 has 16 divisors (see below), whose sum is σ = 43843104. Its totient is φ = 7217424.

The previous prime is 21786899. The next prime is 21786907. The reversal of 21786906 is 60968712.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21786907) by changing a digit.

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, 10161 + ... + 12116.

It is an arithmetic number, because the mean of its divisors is an integer number (2740194).

Almost surely, 2^21786906 is an apocalyptic number.

21786906 is an abundant number, since it is smaller than the sum of its proper divisors (22056198).

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

21786906 is a wasteful number, since it uses less digits than its factorization.

21786906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22445.

The product of its (nonzero) digits is 36288, while the sum is 39.

The square root of 21786906 is about 4667.6445880122. The cubic root of 21786906 is about 279.2963026740.

The spelling of 21786906 in words is "twenty-one million, seven hundred eighty-six thousand, nine hundred six".