21027009 has 16 divisors (see below), whose sum is σ = 28497920. Its totient is φ = 13789440.

The previous prime is 21027007. The next prime is 21027031. The reversal of 21027009 is 90072012.

It is a happy number.

It is not a de Polignac number, because 21027009 - 2¹ = 21027007 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21027007) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87129 + ... + 87369.

It is an arithmetic number, because the mean of its divisors is an integer number (1781120).

Almost surely, 2^21027009 is an apocalyptic number.

It is an amenable number.

21027009 is a deficient number, since it is larger than the sum of its proper divisors (7470911).

21027009 is a wasteful number, since it uses less digits than its factorization.

21027009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 600.

The product of its (nonzero) digits is 252, while the sum is 21.

The square root of 21027009 is about 4585.5216715222. The cubic root of 21027009 is about 276.0106459872.

The spelling of 21027009 in words is "twenty-one million, twenty-seven thousand, nine".