21365806 has 16 divisors (see below), whose sum is σ = 39957120. Its totient is φ = 8324280.

The previous prime is 21365801. The next prime is 21365809. The reversal of 21365806 is 60856312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21365801) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69216 + ... + 69523.

It is an arithmetic number, because the mean of its divisors is an integer number (2497320).

Almost surely, 2^21365806 is an apocalyptic number.

21365806 is a deficient number, since it is larger than the sum of its proper divisors (18591314).

21365806 is a wasteful number, since it uses less digits than its factorization.

21365806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138759.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21365806 is about 4622.3160861196. The cubic root of 21365806 is about 277.4851589606.

The spelling of 21365806 in words is "twenty-one million, three hundred sixty-five thousand, eight hundred six".