99997981 has 2 divisors, whose sum is σ = 99997982. Its totient is φ = 99997980.

The previous prime is 99997973. The next prime is 99998021. The reversal of 99997981 is 18979999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 74545956 + 25452025 = 8634^2 + 5045^2 .

It is an emirp because it is prime and its reverse (18979999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 99997981 - 2³ = 99997973 is a prime.

It is a super-2 number, since 2×99997981² = 19999192408152722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99997901) 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, 49998990 + 49998991.

It is an arithmetic number, because the mean of its divisors is an integer number (49998991).

Almost surely, 2^99997981 is an apocalyptic number.

It is an amenable number.

99997981 is a deficient number, since it is larger than the sum of its proper divisors (1).

99997981 is an equidigital number, since it uses as much as digits as its factorization.

99997981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3306744, while the sum is 61.

The square root of 99997981 is about 9999.8990494904. The cubic root of 99997981 is about 464.1557595510.

The spelling of 99997981 in words is "ninety-nine million, nine hundred ninety-seven thousand, nine hundred eighty-one".