21556406 has 8 divisors (see below), whose sum is σ = 33123384. Its totient is φ = 10515280.

The previous prime is 21556397. The next prime is 21556421. The reversal of 21556406 is 60465512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 131360 + ... + 131523.

It is an arithmetic number, because the mean of its divisors is an integer number (4140423).

Almost surely, 2^21556406 is an apocalyptic number.

21556406 is a deficient number, since it is larger than the sum of its proper divisors (11566978).

21556406 is a wasteful number, since it uses less digits than its factorization.

21556406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 262926.

The product of its (nonzero) digits is 7200, while the sum is 29.

The square root of 21556406 is about 4642.8876790205. The cubic root of 21556406 is about 278.3078469578.

The spelling of 21556406 in words is "twenty-one million, five hundred fifty-six thousand, four hundred six".