21857808 has 40 divisors (see below), whose sum is σ = 64533568. Its totient is φ = 6244992.

The previous prime is 21857807. The next prime is 21857813. The reversal of 21857808 is 80875812.

It is not an unprimeable number, because it can be changed into a prime (21857807) 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, 32191 + ... + 32862.

Almost surely, 2^21857808 is an apocalyptic number.

21857808 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21857808 is an abundant number, since it is smaller than the sum of its proper divisors (42675760).

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

21857808 is a wasteful number, since it uses less digits than its factorization.

21857808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65071 (or 65065 counting only the distinct ones).

The product of its (nonzero) digits is 35840, while the sum is 39.

The square root of 21857808 is about 4675.2334701061. The cubic root of 21857808 is about 279.5989496503.

The spelling of 21857808 in words is "twenty-one million, eight hundred fifty-seven thousand, eight hundred eight".