21809376 has 72 divisors (see below), whose sum is σ = 63567504. Its totient is φ = 7088640.

The previous prime is 21809357. The next prime is 21809377. The reversal of 21809376 is 67390812.

It is a tau number, because it is divible by the number of its divisors (72).

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 21809376.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21809377) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10885 + ... + 12731.

It is an arithmetic number, because the mean of its divisors is an integer number (882882).

Almost surely, 2^21809376 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 21809376, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31783752).

21809376 is an abundant number, since it is smaller than the sum of its proper divisors (41758128).

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

21809376 is a wasteful number, since it uses less digits than its factorization.

21809376 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1904 (or 1893 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21809376 is about 4670.0509633194. The cubic root of 21809376 is about 279.3922874158.

The spelling of 21809376 in words is "twenty-one million, eight hundred nine thousand, three hundred seventy-six".