66905381 has 2 divisors, whose sum is σ = 66905382. Its totient is φ = 66905380.

The previous prime is 66905341. The next prime is 66905429. The reversal of 66905381 is 18350966.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56761156 + 10144225 = 7534^2 + 3185^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66905381 is a prime.

It is a super-2 number, since 2×66905381² = 8952660013510322, which contains 22 as substring.

It is a Sophie Germain 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 (66905341) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33452690 + 33452691.

It is an arithmetic number, because the mean of its divisors is an integer number (33452691).

Almost surely, 2^66905381 is an apocalyptic number.

It is an amenable number.

66905381 is a deficient number, since it is larger than the sum of its proper divisors (1).

66905381 is an equidigital number, since it uses as much as digits as its factorization.

66905381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 66905381 is about 8179.5709545183. The cubic root of 66905381 is about 405.9635261304.

The spelling of 66905381 in words is "sixty-six million, nine hundred five thousand, three hundred eighty-one".