998775657521 has 2 divisors, whose sum is σ = 998775657522. Its totient is φ = 998775657520.

The previous prime is 998775657463. The next prime is 998775657533. The reversal of 998775657521 is 125756577899.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 983141656225 + 15634001296 = 991535^2 + 125036^2 .

It is an emirp because it is prime and its reverse (125756577899) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 998775657521 - 2⁶ = 998775657457 is a prime.

It is not a weakly prime, because it can be changed into another prime (998775647521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499387828760 + 499387828761.

It is an arithmetic number, because the mean of its divisors is an integer number (499387828761).

Almost surely, 2^998775657521 is an apocalyptic number.

It is an amenable number.

998775657521 is a deficient number, since it is larger than the sum of its proper divisors (1).

998775657521 is an equidigital number, since it uses as much as digits as its factorization.

998775657521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 333396000, while the sum is 71.

The spelling of 998775657521 in words is "nine hundred ninety-eight billion, seven hundred seventy-five million, six hundred fifty-seven thousand, five hundred twenty-one".