21321009 has 16 divisors (see below), whose sum is σ = 33445440. Its totient is φ = 13377600.

The previous prime is 21320987. The next prime is 21321019. The reversal of 21321009 is 90012312.

It is a happy number.

It is not a de Polignac number, because 21321009 - 2⁷ = 21320881 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21320982 and 21321000.

It is not an unprimeable number, because it can be changed into a prime (21321019) 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 15 ways as a sum of consecutive naturals, for example, 22767 + ... + 23684.

It is an arithmetic number, because the mean of its divisors is an integer number (2090340).

Almost surely, 2^21321009 is an apocalyptic number.

It is an amenable number.

21321009 is a deficient number, since it is larger than the sum of its proper divisors (12124431).

21321009 is a wasteful number, since it uses less digits than its factorization.

21321009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46477 (or 46471 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21321009 is about 4617.4678125570. The cubic root of 21321009 is about 277.2910918557.

The spelling of 21321009 in words is "twenty-one million, three hundred twenty-one thousand, nine".