99993781 has 2 divisors, whose sum is σ = 99993782. Its totient is φ = 99993780.

The previous prime is 99993767. The next prime is 99993787. The reversal of 99993781 is 18739999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64400625 + 35593156 = 8025^2 + 5966^2 .

It is an emirp because it is prime and its reverse (18739999) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 99993781 - 2¹¹ = 99991733 is a prime.

It is a super-2 number, since 2×99993781² = 19997512477351922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99993787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49996890 + 49996891.

It is an arithmetic number, because the mean of its divisors is an integer number (49996891).

Almost surely, 2^99993781 is an apocalyptic number.

It is an amenable number.

99993781 is a deficient number, since it is larger than the sum of its proper divisors (1).

99993781 is an equidigital number, since it uses as much as digits as its factorization.

99993781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1102248, while the sum is 55.

The square root of 99993781 is about 9999.6890451654. The cubic root of 99993781 is about 464.1492611482.

The spelling of 99993781 in words is "ninety-nine million, nine hundred ninety-three thousand, seven hundred eighty-one".