68651981 has 2 divisors, whose sum is σ = 68651982. Its totient is φ = 68651980.

The previous prime is 68651971. The next prime is 68652029. The reversal of 68651981 is 18915686.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 68392900 + 259081 = 8270^2 + 509^2 .

It is a cyclic number.

It is not a de Polignac number, because 68651981 - 2¹⁴ = 68635597 is a prime.

It is a super-2 number, since 2×68651981² = 9426188990448722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (68651971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34325990 + 34325991.

It is an arithmetic number, because the mean of its divisors is an integer number (34325991).

Almost surely, 2^68651981 is an apocalyptic number.

It is an amenable number.

68651981 is a deficient number, since it is larger than the sum of its proper divisors (1).

68651981 is an equidigital number, since it uses as much as digits as its factorization.

68651981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 44.

The square root of 68651981 is about 8285.6490994973. The cubic root of 68651981 is about 409.4658540924.

The spelling of 68651981 in words is "sixty-eight million, six hundred fifty-one thousand, nine hundred eighty-one".