68640581 has 2 divisors, whose sum is σ = 68640582. Its totient is φ = 68640580.

The previous prime is 68640571. The next prime is 68640589. The reversal of 68640581 is 18504686.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 63840100 + 4800481 = 7990^2 + 2191^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-68640581 is a prime.

It is a super-2 number, since 2×68640581² = 9423058720035122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen 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 (68640589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34320290 + 34320291.

It is an arithmetic number, because the mean of its divisors is an integer number (34320291).

Almost surely, 2^68640581 is an apocalyptic number.

It is an amenable number.

68640581 is a deficient number, since it is larger than the sum of its proper divisors (1).

68640581 is an equidigital number, since it uses as much as digits as its factorization.

68640581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46080, while the sum is 38.

The square root of 68640581 is about 8284.9611344894. The cubic root of 68640581 is about 409.4431882297.

The spelling of 68640581 in words is "sixty-eight million, six hundred forty thousand, five hundred eighty-one".