66061381 has 2 divisors, whose sum is σ = 66061382. Its totient is φ = 66061380.

The previous prime is 66061379. The next prime is 66061393. The reversal of 66061381 is 18316066.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55368481 + 10692900 = 7441^2 + 3270^2 .

It is a cyclic number.

It is not a de Polignac number, because 66061381 - 2¹ = 66061379 is a prime.

It is a super-2 number, since 2×66061381² = 8728212119254322, which contains 22 as substring.

Together with 66061379, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66061321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33030690 + 33030691.

It is an arithmetic number, because the mean of its divisors is an integer number (33030691).

Almost surely, 2^66061381 is an apocalyptic number.

66061381 is the 4345-th centered heptagonal number.

It is an amenable number.

66061381 is a deficient number, since it is larger than the sum of its proper divisors (1).

66061381 is an equidigital number, since it uses as much as digits as its factorization.

66061381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5184, while the sum is 31.

The square root of 66061381 is about 8127.8152661093. The cubic root of 66061381 is about 404.2492437264.

The spelling of 66061381 in words is "sixty-six million, sixty-one thousand, three hundred eighty-one".