21199816 has 64 divisors (see below), whose sum is σ = 47278080. Its totient is φ = 8801280.

The previous prime is 21199811. The next prime is 21199831. The reversal of 21199816 is 61899112.

21199816 is a nontrivial binomial coefficient, being equal to C(6512, 2).

It is a Harshad number since it is a multiple of its sum of digits (37).

It is not an unprimeable number, because it can be changed into a prime (21199811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55161 + ... + 55543.

It is an arithmetic number, because the mean of its divisors is an integer number (738720).

Almost surely, 2^21199816 is an apocalyptic number.

21199816 is the 6511-st triangular number and also the 3256-th hexagonal number.

21199816 is the 2171-st centered nonagonal number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21199816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23639040).

21199816 is an abundant number, since it is smaller than the sum of its proper divisors (26078264).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21199816 is a wasteful number, since it uses less digits than its factorization.

21199816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 454 (or 450 counting only the distinct ones).

The product of its digits is 7776, while the sum is 37.

The square root of 21199816 is about 4604.3257921220. The cubic root of 21199816 is about 276.7647000214.

It can be divided in two parts, 2119 and 9816, that added together give a triangular number (11935 = T₁₅₄).

The spelling of 21199816 in words is "twenty-one million, one hundred ninety-nine thousand, eight hundred sixteen".