21906844 has 12 divisors (see below), whose sum is σ = 38400264. Its totient is φ = 10935344.

The previous prime is 21906839. The next prime is 21906847. The reversal of 21906844 is 44860912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21906847) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1582 + ... + 6805.

It is an arithmetic number, because the mean of its divisors is an integer number (3200022).

Almost surely, 2^21906844 is an apocalyptic number.

It is an amenable number.

21906844 is a deficient number, since it is larger than the sum of its proper divisors (16493420).

21906844 is a wasteful number, since it uses less digits than its factorization.

21906844 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9044 (or 9042 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 34.

The square root of 21906844 is about 4680.4747622437. The cubic root of 21906844 is about 279.8078784103.

The spelling of 21906844 in words is "twenty-one million, nine hundred six thousand, eight hundred forty-four".