21579618857 has 2 divisors, whose sum is σ = 21579618858. Its totient is φ = 21579618856.

The previous prime is 21579618811. The next prime is 21579618871. The reversal of 21579618857 is 75881697512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11561410576 + 10018208281 = 107524^2 + 100091^2 .

It is a cyclic number.

It is not a de Polignac number, because 21579618857 - 2¹⁶ = 21579553321 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21579618796 and 21579618805.

It is not a weakly prime, because it can be changed into another prime (21579618887) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10789809428 + 10789809429.

It is an arithmetic number, because the mean of its divisors is an integer number (10789809429).

Almost surely, 2^21579618857 is an apocalyptic number.

It is an amenable number.

21579618857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21579618857 is an equidigital number, since it uses as much as digits as its factorization.

21579618857 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8467200, while the sum is 59.

The spelling of 21579618857 in words is "twenty-one billion, five hundred seventy-nine million, six hundred eighteen thousand, eight hundred fifty-seven".