21217204240 has 40 divisors (see below), whose sum is σ = 51926319360. Its totient is φ = 8040203136.

The previous prime is 21217204237. The next prime is 21217204241. The reversal of 21217204240 is 4240271212.

It is a tau number, because it is divible by the number of its divisors (40).

It is not an unprimeable number, because it can be changed into a prime (21217204241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6977824 + ... + 6980863.

It is an arithmetic number, because the mean of its divisors is an integer number (1298157984).

Almost surely, 2^21217204240 is an apocalyptic number.

21217204240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21217204240 is an abundant number, since it is smaller than the sum of its proper divisors (30709115120).

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

21217204240 is a wasteful number, since it uses less digits than its factorization.

21217204240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13958719 (or 13958713 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 25.

Adding to 21217204240 its reverse (4240271212), we get a palindrome (25457475452).

The spelling of 21217204240 in words is "twenty-one billion, two hundred seventeen million, two hundred four thousand, two hundred forty".