66691693 has 2 divisors, whose sum is σ = 66691694. Its totient is φ = 66691692.

The previous prime is 66691657. The next prime is 66691699. The reversal of 66691693 is 39619666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 64609444 + 2082249 = 8038^2 + 1443^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66691693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66691699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33345846 + 33345847.

It is an arithmetic number, because the mean of its divisors is an integer number (33345847).

Almost surely, 2^66691693 is an apocalyptic number.

It is an amenable number.

66691693 is a deficient number, since it is larger than the sum of its proper divisors (1).

66691693 is an equidigital number, since it uses as much as digits as its factorization.

66691693 is an evil number, because the sum of its binary digits is even.

The product of its digits is 314928, while the sum is 46.

The square root of 66691693 is about 8166.4982091469. The cubic root of 66691693 is about 405.5308650954.

The spelling of 66691693 in words is "sixty-six million, six hundred ninety-one thousand, six hundred ninety-three".