21604398 has 16 divisors (see below), whose sum is σ = 43376256. Its totient is φ = 7173560.

The previous prime is 21604397. The next prime is 21604421. The reversal of 21604398 is 89340612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604393) 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, 5268 + ... + 8423.

It is an arithmetic number, because the mean of its divisors is an integer number (2711016).

Almost surely, 2^21604398 is an apocalyptic number.

21604398 is an abundant number, since it is smaller than the sum of its proper divisors (21771858).

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

21604398 is a wasteful number, since it uses less digits than its factorization.

21604398 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13959.

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 21604398 is about 4648.0531408322. The cubic root of 21604398 is about 278.5142303152.

The spelling of 21604398 in words is "twenty-one million, six hundred four thousand, three hundred ninety-eight".