68721649 has 2 divisors, whose sum is σ = 68721650. Its totient is φ = 68721648.

The previous prime is 68721647. The next prime is 68721659. The reversal of 68721649 is 94612786.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65092624 + 3629025 = 8068^2 + 1905^2 .

It is a cyclic number.

It is not a de Polignac number, because 68721649 - 2¹ = 68721647 is a prime.

Together with 68721647, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (68721647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 34360824 + 34360825.

It is an arithmetic number, because the mean of its divisors is an integer number (34360825).

Almost surely, 2^68721649 is an apocalyptic number.

It is an amenable number.

68721649 is a deficient number, since it is larger than the sum of its proper divisors (1).

68721649 is an equidigital number, since it uses as much as digits as its factorization.

68721649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145152, while the sum is 43.

The square root of 68721649 is about 8289.8521699726. The cubic root of 68721649 is about 409.6043158553.

The spelling of 68721649 in words is "sixty-eight million, seven hundred twenty-one thousand, six hundred forty-nine".