21599765557 has 2 divisors, whose sum is σ = 21599765558. Its totient is φ = 21599765556.

The previous prime is 21599765521. The next prime is 21599765567. The reversal of 21599765557 is 75556799512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16966104516 + 4633661041 = 130254^2 + 68071^2 .

It is a cyclic number.

It is not a de Polignac number, because 21599765557 - 2¹¹ = 21599763509 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21599765495 and 21599765504.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21599765567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10799882778 + 10799882779.

It is an arithmetic number, because the mean of its divisors is an integer number (10799882779).

Almost surely, 2^21599765557 is an apocalyptic number.

It is an amenable number.

21599765557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21599765557 is an equidigital number, since it uses as much as digits as its factorization.

21599765557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 29767500, while the sum is 61.

The spelling of 21599765557 in words is "twenty-one billion, five hundred ninety-nine million, seven hundred sixty-five thousand, five hundred fifty-seven".