21100008 has 16 divisors (see below), whose sum is σ = 52750080. Its totient is φ = 7033328.

The previous prime is 21100007. The next prime is 21100019. The reversal of 21100008 is 80000112.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 21099966 and 21100002.

It is not an unprimeable number, because it can be changed into a prime (21100003) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 439560 + ... + 439607.

It is an arithmetic number, because the mean of its divisors is an integer number (3296880).

Almost surely, 2^21100008 is an apocalyptic number.

It is an amenable number.

21100008 is an abundant number, since it is smaller than the sum of its proper divisors (31650072).

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

21100008 is a wasteful number, since it uses less digits than its factorization.

21100008 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 879176 (or 879172 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 21100008 is about 4593.4745019429. The cubic root of 21100008 is about 276.3296837486.

The spelling of 21100008 in words is "twenty-one million, one hundred thousand, eight".