21597504217 has 2 divisors, whose sum is σ = 21597504218. Its totient is φ = 21597504216.

The previous prime is 21597504211. The next prime is 21597504241. The reversal of 21597504217 is 71240579512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20994850816 + 602653401 = 144896^2 + 24549^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21597504217 is a prime.

It is not a weakly prime, because it can be changed into another prime (21597504211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10798752108 + 10798752109.

It is an arithmetic number, because the mean of its divisors is an integer number (10798752109).

Almost surely, 2^21597504217 is an apocalyptic number.

It is an amenable number.

21597504217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21597504217 is an equidigital number, since it uses as much as digits as its factorization.

21597504217 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 176400, while the sum is 43.

The spelling of 21597504217 in words is "twenty-one billion, five hundred ninety-seven million, five hundred four thousand, two hundred seventeen".