19721216 has 22 divisors (see below), whose sum is σ = 39425220. Its totient is φ = 9860096.

The previous prime is 19721213. The next prime is 19721227. The reversal of 19721216 is 61212791.

It is not an unprimeable number, because it can be changed into a prime (19721213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8606 + ... + 10653.

Almost surely, 2^19721216 is an apocalyptic number.

19721216 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

19721216 is a deficient number, since it is larger than the sum of its proper divisors (19704004).

19721216 is an equidigital number, since it uses as much as digits as its factorization.

19721216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19279 (or 19261 counting only the distinct ones).

The product of its digits is 1512, while the sum is 29.

The square root of 19721216 is about 4440.8575748384. The cubic root of 19721216 is about 270.1746286858.

The spelling of 19721216 in words is "nineteen million, seven hundred twenty-one thousand, two hundred sixteen".