21321409 has 8 divisors (see below), whose sum is σ = 22527360. Its totient is φ = 20146896.

The previous prime is 21321407. The next prime is 21321431. The reversal of 21321409 is 90412312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21321409 - 2¹ = 21321407 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21321409.

It is not an unprimeable number, because it can be changed into a prime (21321407) 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 7 ways as a sum of consecutive naturals, for example, 6459 + ... + 9184.

It is an arithmetic number, because the mean of its divisors is an integer number (2815920).

Almost surely, 2^21321409 is an apocalyptic number.

21321409 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21321409 is a deficient number, since it is larger than the sum of its proper divisors (1205951).

21321409 is a wasteful number, since it uses less digits than its factorization.

21321409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15719.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 21321409 is about 4617.5111261371. The cubic root of 21321409 is about 277.2928259160.

The spelling of 21321409 in words is "twenty-one million, three hundred twenty-one thousand, four hundred nine".