99957777921 has 15 divisors (see below), whose sum is σ = 149323894291. Its totient is φ = 66636621648.

The previous prime is 99957777853. The next prime is 99957777923. The reversal of 99957777921 is 12977775999.

The square root of 99957777921 is 316161.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 6101328321 + 93856449600 = 78111^2 + 306360^2 .

It is not a de Polignac number, because 99957777921 - 2⁷ = 99957777793 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 99957777921.

It is not an unprimeable number, because it can be changed into a prime (99957777923) 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 in 14 ways as a sum of consecutive naturals, for example, 2827885 + ... + 2863013.

Almost surely, 2^99957777921 is an apocalyptic number.

99957777921 is the 316161-st square number.

99957777921 is the 158081-st centered octagonal number.

It is an amenable number.

99957777921 is a deficient number, since it is larger than the sum of its proper divisors (49366116370).

99957777921 is an frugal number, since it uses more digits than its factorization.

99957777921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70270 (or 35132 counting only the distinct ones).

The product of its digits is 157529610, while the sum is 72.

The spelling of 99957777921 in words is "ninety-nine billion, nine hundred fifty-seven million, seven hundred seventy-seven thousand, nine hundred twenty-one".