21003668 has 12 divisors (see below), whose sum is σ = 42007392. Its totient is φ = 9001560.

The previous prime is 21003667. The next prime is 21003673. The reversal of 21003668 is 86630012.

21003668 is an admirable number.

It is a hoax number, since the sum of its digits (26) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 375038 + ... + 375093.

It is an arithmetic number, because the mean of its divisors is an integer number (3500616).

Almost surely, 2^21003668 is an apocalyptic number.

21003668 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21003668 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21003668 is a wasteful number, since it uses less digits than its factorization.

21003668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 750142 (or 750140 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 21003668 is about 4582.9758890922. The cubic root of 21003668 is about 275.9084797726.

The spelling of 21003668 in words is "twenty-one million, three thousand, six hundred sixty-eight".