21517581679 has 8 divisors (see below), whose sum is σ = 23658559488. Its totient is φ = 19407409560.

The previous prime is 21517581677. The next prime is 21517581721. The reversal of 21517581679 is 97618571512.

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

It is not a de Polignac number, because 21517581679 - 2¹ = 21517581677 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21517581677) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 7699957 + ... + 7702750.

It is an arithmetic number, because the mean of its divisors is an integer number (2957319936).

Almost surely, 2^21517581679 is an apocalyptic number.

21517581679 is a deficient number, since it is larger than the sum of its proper divisors (2140977809).

21517581679 is a wasteful number, since it uses less digits than its factorization.

21517581679 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15402845.

The product of its digits is 1058400, while the sum is 52.

The spelling of 21517581679 in words is "twenty-one billion, five hundred seventeen million, five hundred eighty-one thousand, six hundred seventy-nine".