21308868 has 36 divisors (see below), whose sum is σ = 61559680. Its totient is φ = 6088176.

The previous prime is 21308867. The next prime is 21308887. The reversal of 21308868 is 86880312.

It is a tau number, because it is divible by the number of its divisors (36).

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

It is not an unprimeable number, because it can be changed into a prime (21308867) 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, 42028 + ... + 42531.

Almost surely, 2^21308868 is an apocalyptic number.

21308868 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21308868 is an abundant number, since it is smaller than the sum of its proper divisors (40250812).

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

21308868 is a wasteful number, since it uses less digits than its factorization.

21308868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 84576 (or 84571 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 21308868 is about 4616.1529437401. The cubic root of 21308868 is about 277.2384484689.

The spelling of 21308868 in words is "twenty-one million, three hundred eight thousand, eight hundred sixty-eight".