99987721 has 2 divisors, whose sum is σ = 99987722. Its totient is φ = 99987720.

The previous prime is 99987707. The next prime is 99987763. The reversal of 99987721 is 12778999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 61795321 + 38192400 = 7861^2 + 6180^2 .

It is an emirp because it is prime and its reverse (12778999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 99987721 - 2⁷ = 99987593 is a prime.

It is a nialpdrome in base 10.

It is not a weakly prime, because it can be changed into another prime (99987781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49993860 + 49993861.

It is an arithmetic number, because the mean of its divisors is an integer number (49993861).

Almost surely, 2^99987721 is an apocalyptic number.

It is an amenable number.

99987721 is a deficient number, since it is larger than the sum of its proper divisors (1).

99987721 is an equidigital number, since it uses as much as digits as its factorization.

99987721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 571536, while the sum is 52.

The square root of 99987721 is about 9999.3860311521. The cubic root of 99987721 is about 464.1398845605.

The spelling of 99987721 in words is "ninety-nine million, nine hundred eighty-seven thousand, seven hundred twenty-one".