21217912 has 16 divisors (see below), whose sum is σ = 39957840. Its totient is φ = 10562496.

The previous prime is 21217907. The next prime is 21217943. The reversal of 21217912 is 21971212.

It is a congruent number.

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 in 3 ways as a sum of consecutive naturals, for example, 3828 + ... + 7555.

It is an arithmetic number, because the mean of its divisors is an integer number (2497365).

Almost surely, 2^21217912 is an apocalyptic number.

It is an amenable number.

21217912 is a deficient number, since it is larger than the sum of its proper divisors (18739928).

21217912 is a wasteful number, since it uses less digits than its factorization.

21217912 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11622 (or 11618 counting only the distinct ones).

The product of its digits is 504, while the sum is 25.

The square root of 21217912 is about 4606.2904815046. The cubic root of 21217912 is about 276.8434256993.

The spelling of 21217912 in words is "twenty-one million, two hundred seventeen thousand, nine hundred twelve".