21906438 has 32 divisors (see below), whose sum is σ = 46611936. Its totient is φ = 6839808.

The previous prime is 21906413. The next prime is 21906461. The reversal of 21906438 is 83460912.

It is a junction number, because it is equal to n+sod(n) for n = 21906399 and 21906408.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29520 + ... + 30252.

It is an arithmetic number, because the mean of its divisors is an integer number (1456623).

Almost surely, 2^21906438 is an apocalyptic number.

21906438 is an abundant number, since it is smaller than the sum of its proper divisors (24705498).

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

21906438 is a wasteful number, since it uses less digits than its factorization.

21906438 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1048.

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21906438 is about 4680.4313903742. The cubic root of 21906438 is about 279.8061498378.

The spelling of 21906438 in words is "twenty-one million, nine hundred six thousand, four hundred thirty-eight".