21538806 has 8 divisors (see below), whose sum is σ = 43077624. Its totient is φ = 7179600.

The previous prime is 21538789. The next prime is 21538841. The reversal of 21538806 is 60883512.

It is a happy number.

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

21538806 is an admirable number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1794895 + ... + 1794906.

It is an arithmetic number, because the mean of its divisors is an integer number (5384703).

Almost surely, 2^21538806 is an apocalyptic number.

21538806 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.

21538806 is a wasteful number, since it uses less digits than its factorization.

21538806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3589806.

The product of its (nonzero) digits is 11520, while the sum is 33.

The square root of 21538806 is about 4640.9919198378. The cubic root of 21538806 is about 278.2320836822.

The spelling of 21538806 in words is "twenty-one million, five hundred thirty-eight thousand, eight hundred six".