16821409 has 8 divisors (see below), whose sum is σ = 18462528. Its totient is φ = 15198960.

The previous prime is 16821407. The next prime is 16821433. The reversal of 16821409 is 90412861.

It is a happy number.

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 16821409 - 2¹ = 16821407 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16821401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2742 + ... + 6415.

It is an arithmetic number, because the mean of its divisors is an integer number (2307816).

Almost surely, 2^16821409 is an apocalyptic number.

It is an amenable number.

16821409 is a deficient number, since it is larger than the sum of its proper divisors (1641119).

16821409 is a wasteful number, since it uses less digits than its factorization.

16821409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9335.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 16821409 is about 4101.3911054665. The cubic root of 16821409 is about 256.2245801475.

The spelling of 16821409 in words is "sixteen million, eight hundred twenty-one thousand, four hundred nine".