21308906 has 8 divisors (see below), whose sum is σ = 31989504. Its totient is φ = 10645740.

The previous prime is 21308897. The next prime is 21308921. The reversal of 21308906 is 60980312.

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

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, 680 + ... + 6563.

It is an arithmetic number, because the mean of its divisors is an integer number (3998688).

Almost surely, 2^21308906 is an apocalyptic number.

21308906 is a deficient number, since it is larger than the sum of its proper divisors (10680598).

21308906 is a wasteful number, since it uses less digits than its factorization.

21308906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8716.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21308906 is about 4616.1570597197. The cubic root of 21308906 is about 277.2386132682.

The spelling of 21308906 in words is "twenty-one million, three hundred eight thousand, nine hundred six".