21206806 has 8 divisors (see below), whose sum is σ = 31833360. Its totient is φ = 10595688.

The previous prime is 21206797. The next prime is 21206807. The reversal of 21206806 is 60860212.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21206807) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 615 + ... + 6541.

It is an arithmetic number, because the mean of its divisors is an integer number (3979170).

Almost surely, 2^21206806 is an apocalyptic number.

21206806 is a deficient number, since it is larger than the sum of its proper divisors (10626554).

21206806 is a wasteful number, since it uses less digits than its factorization.

21206806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7718.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21206806 is about 4605.0847983506. The cubic root of 21206806 is about 276.7951149499.

The spelling of 21206806 in words is "twenty-one million, two hundred six thousand, eight hundred six".