66666381 has 8 divisors (see below), whose sum is σ = 88947360. Its totient is φ = 44414832.

The previous prime is 66666371. The next prime is 66666409. The reversal of 66666381 is 18366666.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66666381 - 2⁶ = 66666317 is a prime.

It is a super-2 number, since 2×66666381² = 8888812711274322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66666311) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1375 + ... + 11628.

It is an arithmetic number, because the mean of its divisors is an integer number (11118420).

Almost surely, 2^66666381 is an apocalyptic number.

It is an amenable number.

66666381 is a deficient number, since it is larger than the sum of its proper divisors (22280979).

66666381 is a wasteful number, since it uses less digits than its factorization.

66666381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14715.

The product of its digits is 186624, while the sum is 42.

The square root of 66666381 is about 8164.9483158193. The cubic root of 66666381 is about 405.4795538766.

The spelling of 66666381 in words is "sixty-six million, six hundred sixty-six thousand, three hundred eighty-one".