66616691 has 2 divisors, whose sum is σ = 66616692. Its totient is φ = 66616690.

The previous prime is 66616663. The next prime is 66616699. The reversal of 66616691 is 19661666.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 66616691 - 2¹⁰ = 66615667 is a prime.

It is not a weakly prime, because it can be changed into another prime (66616699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33308345 + 33308346.

It is an arithmetic number, because the mean of its divisors is an integer number (33308346).

Almost surely, 2^66616691 is an apocalyptic number.

66616691 is a deficient number, since it is larger than the sum of its proper divisors (1).

66616691 is an equidigital number, since it uses as much as digits as its factorization.

66616691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 41.

The square root of 66616691 is about 8161.9048634495. The cubic root of 66616691 is about 405.3787870100.

The spelling of 66616691 in words is "sixty-six million, six hundred sixteen thousand, six hundred ninety-one".