21701815217 has 8 divisors (see below), whose sum is σ = 21811320360. Its totient is φ = 21592524160.

The previous prime is 21701815151. The next prime is 21701815231. The reversal of 21701815217 is 71251810712.

It can be written as a sum of positive squares in 4 ways, for example, as 1845905296 + 19855909921 = 42964^2 + 140911^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21701815217 - 2²⁰ = 21700766641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21701815237) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 151703 + ... + 257715.

It is an arithmetic number, because the mean of its divisors is an integer number (2726415045).

Almost surely, 2^21701815217 is an apocalyptic number.

It is an amenable number.

21701815217 is a deficient number, since it is larger than the sum of its proper divisors (109505143).

21701815217 is a wasteful number, since it uses less digits than its factorization.

21701815217 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107043.

The product of its (nonzero) digits is 7840, while the sum is 35.

The spelling of 21701815217 in words is "twenty-one billion, seven hundred one million, eight hundred fifteen thousand, two hundred seventeen".