21205398 has 16 divisors (see below), whose sum is σ = 42548400. Its totient is φ = 7045536.

The previous prime is 21205397. The next prime is 21205399. The reversal of 21205398 is 89350212.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21205397) and next prime (21205399).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205391) 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, 3673 + ... + 7476.

It is an arithmetic number, because the mean of its divisors is an integer number (2659275).

Almost surely, 2^21205398 is an apocalyptic number.

21205398 is an abundant number, since it is smaller than the sum of its proper divisors (21343002).

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

21205398 is a wasteful number, since it uses less digits than its factorization.

21205398 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11471.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 21205398 is about 4604.9319213209. The cubic root of 21205398 is about 276.7889889897.

The spelling of 21205398 in words is "twenty-one million, two hundred five thousand, three hundred ninety-eight".