21208755835617 has 16 divisors (see below), whose sum is σ = 32319921242112. Its totient is φ = 12118607632080.

The previous prime is 21208755835607. The next prime is 21208755835621. The reversal of 21208755835617 is 71653855780212.

It is a happy number.

It is not a de Polignac number, because 21208755835617 - 2⁸ = 21208755835361 is a prime.

It is a super-2 number, since 2×21208755835617² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21208755835607) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28009863 + ... + 28757084.

It is an arithmetic number, because the mean of its divisors is an integer number (2019995077632).

Almost surely, 2^{21208755835617} is an apocalyptic number.

It is an amenable number.

21208755835617 is a deficient number, since it is larger than the sum of its proper divisors (11111165406495).

21208755835617 is a wasteful number, since it uses less digits than its factorization.

21208755835617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56784748.

The product of its (nonzero) digits is 28224000, while the sum is 60.

The spelling of 21208755835617 in words is "twenty-one trillion, two hundred eight billion, seven hundred fifty-five million, eight hundred thirty-five thousand, six hundred seventeen".