21721929518 has 8 divisors (see below), whose sum is σ = 32594678112. Its totient is φ = 10857036816.

The previous prime is 21721929461. The next prime is 21721929521. The reversal of 21721929518 is 81592912712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1957055 + ... + 1968122.

It is an arithmetic number, because the mean of its divisors is an integer number (4074334764).

Almost surely, 2^21721929518 is an apocalyptic number.

21721929518 is a deficient number, since it is larger than the sum of its proper divisors (10872748594).

21721929518 is a wasteful number, since it uses less digits than its factorization.

21721929518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3927946.

The product of its digits is 181440, while the sum is 47.

The spelling of 21721929518 in words is "twenty-one billion, seven hundred twenty-one million, nine hundred twenty-nine thousand, five hundred eighteen".