21129808 has 40 divisors (see below), whose sum is σ = 47371968. Its totient is φ = 8942592.

The previous prime is 21129803. The next prime is 21129809. The reversal of 21129808 is 80892112.

It is a happy number.

It is a super-2 number, since 2×21129808² = 892937572233728, 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 21129808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21129803) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8160 + ... + 10432.

Almost surely, 2^21129808 is an apocalyptic number.

21129808 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 21129808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23685984).

21129808 is an abundant number, since it is smaller than the sum of its proper divisors (26242160).

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

21129808 is a wasteful number, since it uses less digits than its factorization.

21129808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2371 (or 2365 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 31.

The square root of 21129808 is about 4596.7170894020. The cubic root of 21129808 is about 276.4597113608.

The spelling of 21129808 in words is "twenty-one million, one hundred twenty-nine thousand, eight hundred eight".