21009168 has 30 divisors (see below), whose sum is σ = 58796894. Its totient is φ = 7003008.

The previous prime is 21009167. The next prime is 21009173. The reversal of 21009168 is 86190012.

It can be written as a sum of positive squares in only one way, i.e., 16548624 + 4460544 = 4068^2 + 2112^2 .

It is not an unprimeable number, because it can be changed into a prime (21009167) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 72805 + ... + 73092.

Almost surely, 2^21009168 is an apocalyptic number.

It is an amenable number.

21009168 is an abundant number, since it is smaller than the sum of its proper divisors (37787726).

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

21009168 is a wasteful number, since it uses less digits than its factorization.

21009168 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145911 (or 145902 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 21009168 is about 4583.5758966117. The cubic root of 21009168 is about 275.9325607125.

The spelling of 21009168 in words is "twenty-one million, nine thousand, one hundred sixty-eight".