66968681 has 4 divisors (see below), whose sum is σ = 72120132. Its totient is φ = 61817232.

The previous prime is 66968677. The next prime is 66968683. The reversal of 66968681 is 18686966.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 24601600 + 42367081 = 4960^2 + 6509^2 .

It is a cyclic number.

It is not a de Polignac number, because 66968681 - 2² = 66968677 is a prime.

It is a super-2 number, since 2×66968681² = 8969608469759522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66968683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2575706 + ... + 2575731.

It is an arithmetic number, because the mean of its divisors is an integer number (18030033).

Almost surely, 2^66968681 is an apocalyptic number.

It is an amenable number.

66968681 is a deficient number, since it is larger than the sum of its proper divisors (5151451).

66968681 is a wasteful number, since it uses less digits than its factorization.

66968681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5151450.

The product of its digits is 746496, while the sum is 50.

The square root of 66968681 is about 8183.4394358363. The cubic root of 66968681 is about 406.0915147956.

The spelling of 66968681 in words is "sixty-six million, nine hundred sixty-eight thousand, six hundred eighty-one".