68999981 has 2 divisors, whose sum is σ = 68999982. Its totient is φ = 68999980.

The previous prime is 68999971. The next prime is 69000047. The reversal of 68999981 is 18999986.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 61763881 + 7236100 = 7859^2 + 2690^2 .

It is a cyclic number.

It is not a de Polignac number, because 68999981 - 2¹⁰ = 68998957 is a prime.

It is a super-2 number, since 2×68999981² = 9521994756000722, which contains 22 as substring.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 68999981.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (68999951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34499990 + 34499991.

It is an arithmetic number, because the mean of its divisors is an integer number (34499991).

Almost surely, 2^68999981 is an apocalyptic number.

It is an amenable number.

68999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

68999981 is an equidigital number, since it uses as much as digits as its factorization.

68999981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2519424, while the sum is 59.

The square root of 68999981 is about 8306.6227192524. The cubic root of 68999981 is about 410.1565553230.

The spelling of 68999981 in words is "sixty-eight million, nine hundred ninety-nine thousand, nine hundred eighty-one".