21690805 has 8 divisors (see below), whose sum is σ = 26343072. Its totient is φ = 17143248.

The previous prime is 21690803. The next prime is 21690821. The reversal of 21690805 is 50809612.

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

It is a cyclic number.

It is not a de Polignac number, because 21690805 - 2¹ = 21690803 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690803) 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, 25719 + ... + 26548.

It is an arithmetic number, because the mean of its divisors is an integer number (3292884).

Almost surely, 2^21690805 is an apocalyptic number.

It is an amenable number.

21690805 is a deficient number, since it is larger than the sum of its proper divisors (4652267).

21690805 is an equidigital number, since it uses as much as digits as its factorization.

21690805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52355.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 21690805 is about 4657.3388324235. The cubic root of 21690805 is about 278.8850431885.

The spelling of 21690805 in words is "twenty-one million, six hundred ninety thousand, eight hundred five".