21171996 has 96 divisors (see below), whose sum is σ = 57953280. Its totient is φ = 6676992.

The previous prime is 21171991. The next prime is 21172003. The reversal of 21171996 is 69917112.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21171996.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21171991) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 218220 + ... + 218316.

It is an arithmetic number, because the mean of its divisors is an integer number (603680).

Almost surely, 2^21171996 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21171996, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28976640).

21171996 is an abundant number, since it is smaller than the sum of its proper divisors (36781284).

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

21171996 is a wasteful number, since it uses less digits than its factorization.

21171996 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200 (or 192 counting only the distinct ones).

The product of its digits is 6804, while the sum is 36.

The square root of 21171996 is about 4601.3037282927. The cubic root of 21171996 is about 276.6435831776.

The spelling of 21171996 in words is "twenty-one million, one hundred seventy-one thousand, nine hundred ninety-six".