67811561 has 2 divisors, whose sum is σ = 67811562. Its totient is φ = 67811560.

The previous prime is 67811543. The next prime is 67811587. The reversal of 67811561 is 16511876.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 47955625 + 19855936 = 6925^2 + 4456^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-67811561 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (67811531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33905780 + 33905781.

It is an arithmetic number, because the mean of its divisors is an integer number (33905781).

Almost surely, 2^67811561 is an apocalyptic number.

It is an amenable number.

67811561 is a deficient number, since it is larger than the sum of its proper divisors (1).

67811561 is an equidigital number, since it uses as much as digits as its factorization.

67811561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10080, while the sum is 35.

The square root of 67811561 is about 8234.7775319070. Note that the first 3 decimals coincide. The cubic root of 67811561 is about 407.7881304982.

The spelling of 67811561 in words is "sixty-seven million, eight hundred eleven thousand, five hundred sixty-one".