21791308 has 48 divisors (see below), whose sum is σ = 47980800. Its totient is φ = 8412480.

The previous prime is 21791293. The next prime is 21791311. The reversal of 21791308 is 80319712.

It is a super-2 number, since 2×21791308² = 949722208701728, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21791308.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 42558 + ... + 43066.

It is an arithmetic number, because the mean of its divisors is an integer number (999600).

Almost surely, 2^21791308 is an apocalyptic number.

21791308 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 21791308, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23990400).

21791308 is an abundant number, since it is smaller than the sum of its proper divisors (26189492).

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

21791308 is a wasteful number, since it uses less digits than its factorization.

21791308 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 670 (or 668 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21791308 is about 4668.1161082390. The cubic root of 21791308 is about 279.3151118237.

The spelling of 21791308 in words is "twenty-one million, seven hundred ninety-one thousand, three hundred eight".