21205500240 has 160 divisors (see below), whose sum is σ = 69318241920. Its totient is φ = 5347786752.

The previous prime is 21205500223. The next prime is 21205500269. The reversal of 21205500240 is 4200550212.

It is a happy number.

It is a super-3 number, since 3×21205500240³ (a number of 32 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2809752 + ... + 2817288.

It is an arithmetic number, because the mean of its divisors is an integer number (433239012).

Almost surely, 2^21205500240 is an apocalyptic number.

21205500240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21205500240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34659120960).

21205500240 is an abundant number, since it is smaller than the sum of its proper divisors (48112741680).

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

21205500240 is a wasteful number, since it uses less digits than its factorization.

21205500240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8189 (or 8183 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The spelling of 21205500240 in words is "twenty-one billion, two hundred five million, five hundred thousand, two hundred forty".