99870781 has 2 divisors, whose sum is σ = 99870782. Its totient is φ = 99870780.

The previous prime is 99870779. The next prime is 99870787. The reversal of 99870781 is 18707899.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69455556 + 30415225 = 8334^2 + 5515^2 .

It is a cyclic number.

It is not a de Polignac number, because 99870781 - 2¹ = 99870779 is a prime.

It is a super-2 number, since 2×99870781² = 19948345795099922, which contains 22 as substring.

Together with 99870779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99870787) 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, 49935390 + 49935391.

It is an arithmetic number, because the mean of its divisors is an integer number (49935391).

Almost surely, 2^99870781 is an apocalyptic number.

It is an amenable number.

99870781 is a deficient number, since it is larger than the sum of its proper divisors (1).

99870781 is an equidigital number, since it uses as much as digits as its factorization.

99870781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 254016, while the sum is 49.

The square root of 99870781 is about 9993.5369614566. The cubic root of 99870781 is about 463.9588700290.

The spelling of 99870781 in words is "ninety-nine million, eight hundred seventy thousand, seven hundred eighty-one".