21906836 has 12 divisors (see below), whose sum is σ = 43813728. Its totient is φ = 9388632.

The previous prime is 21906821. The next prime is 21906839. The reversal of 21906836 is 63860912.

21906836 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21906796 and 21906805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906839) 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 3 ways as a sum of consecutive naturals, for example, 391166 + ... + 391221.

It is an arithmetic number, because the mean of its divisors is an integer number (3651144).

Almost surely, 2^21906836 is an apocalyptic number.

It is an amenable number.

21906836 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21906836 is a wasteful number, since it uses less digits than its factorization.

21906836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 782398 (or 782396 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 21906836 is about 4680.4739076294. The cubic root of 21906836 is about 279.8078443500.

The spelling of 21906836 in words is "twenty-one million, nine hundred six thousand, eight hundred thirty-six".