21971208 has 128 divisors (see below), whose sum is σ = 68256000. Its totient is φ = 5870592.

The previous prime is 21971197. The next prime is 21971221. The reversal of 21971208 is 80217912.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 139866 + ... + 140022.

It is an arithmetic number, because the mean of its divisors is an integer number (533250).

Almost surely, 2^21971208 is an apocalyptic number.

21971208 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21971208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34128000).

21971208 is an abundant number, since it is smaller than the sum of its proper divisors (46284792).

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

21971208 is a wasteful number, since it uses less digits than its factorization.

21971208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 204 (or 186 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21971208 is about 4687.3455174544. The cubic root of 21971208 is about 280.0816428588.

The spelling of 21971208 in words is "twenty-one million, nine hundred seventy-one thousand, two hundred eight".