21690835 has 4 divisors (see below), whose sum is σ = 26029008. Its totient is φ = 17352664.

The previous prime is 21690821. The next prime is 21690853. The reversal of 21690835 is 53809612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21690835 - 2⁵ = 21690803 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21690835.

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, 2169079 + ... + 2169088.

It is an arithmetic number, because the mean of its divisors is an integer number (6507252).

Almost surely, 2^21690835 is an apocalyptic number.

21690835 is a deficient number, since it is larger than the sum of its proper divisors (4338173).

21690835 is an equidigital number, since it uses as much as digits as its factorization.

21690835 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4338172.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 21690835 is about 4657.3420531458. The cubic root of 21690835 is about 278.8851717614.

The spelling of 21690835 in words is "twenty-one million, six hundred ninety thousand, eight hundred thirty-five".