21128908 has 6 divisors (see below), whose sum is σ = 36975596. Its totient is φ = 10564452.

The previous prime is 21128873. The next prime is 21128917. The reversal of 21128908 is 80982112.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21128908.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2641110 + ... + 2641117.

Almost surely, 2^21128908 is an apocalyptic number.

It is an amenable number.

21128908 is a deficient number, since it is larger than the sum of its proper divisors (15846688).

21128908 is a wasteful number, since it uses less digits than its factorization.

21128908 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5282231 (or 5282229 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 21128908 is about 4596.6191924065. The cubic root of 21128908 is about 276.4557861433.

The spelling of 21128908 in words is "twenty-one million, one hundred twenty-eight thousand, nine hundred eight".