21575838217 has 4 divisors (see below), whose sum is σ = 21587981716. Its totient is φ = 21563694720.

The previous prime is 21575838203. The next prime is 21575838223. The reversal of 21575838217 is 71283857512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7915838841 + 13659999376 = 88971^2 + 116876^2 .

It is a cyclic number.

It is not a de Polignac number, because 21575838217 - 2²³ = 21567449609 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21575838257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6069084 + ... + 6072637.

It is an arithmetic number, because the mean of its divisors is an integer number (5396995429).

Almost surely, 2^21575838217 is an apocalyptic number.

It is an amenable number.

21575838217 is a deficient number, since it is larger than the sum of its proper divisors (12143499).

21575838217 is a wasteful number, since it uses less digits than its factorization.

21575838217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12143498.

The product of its digits is 940800, while the sum is 49.

The spelling of 21575838217 in words is "twenty-one billion, five hundred seventy-five million, eight hundred thirty-eight thousand, two hundred seventeen".