21517608920 has 16 divisors (see below), whose sum is σ = 48414620160. Its totient is φ = 8607043552.

The previous prime is 21517608919. The next prime is 21517608923. The reversal of 21517608920 is 2980671512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21517608923) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 268970072 + ... + 268970151.

It is an arithmetic number, because the mean of its divisors is an integer number (3025913760).

Almost surely, 2^21517608920 is an apocalyptic number.

21517608920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21517608920 is an abundant number, since it is smaller than the sum of its proper divisors (26897011240).

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

21517608920 is a wasteful number, since it uses less digits than its factorization.

21517608920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 537940234 (or 537940230 counting only the distinct ones).

The product of its (nonzero) digits is 60480, while the sum is 41.

The spelling of 21517608920 in words is "twenty-one billion, five hundred seventeen million, six hundred eight thousand, nine hundred twenty".