99999998821 has 2 divisors, whose sum is σ = 99999998822. Its totient is φ = 99999998820.

The previous prime is 99999998767. The next prime is 99999998881. The reversal of 99999998821 is 12889999999.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 83572449921 + 16427548900 = 289089^2 + 128170^2 .

It is an emirp because it is prime and its reverse (12889999999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 99999998821 - 2¹¹ = 99999996773 is a prime.

It is a nialpdrome in base 10.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99999998881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49999999410 + 49999999411.

It is an arithmetic number, because the mean of its divisors is an integer number (49999999411).

Almost surely, 2^99999998821 is an apocalyptic number.

It is an amenable number.

99999998821 is a deficient number, since it is larger than the sum of its proper divisors (1).

99999998821 is an equidigital number, since it uses as much as digits as its factorization.

99999998821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 612220032, while the sum is 82.

The spelling of 99999998821 in words is "ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-eight thousand, eight hundred twenty-one".