66810981 has 8 divisors (see below), whose sum is σ = 90000064. Its totient is φ = 44081280.

The previous prime is 66810967. The next prime is 66811001. The reversal of 66810981 is 18901866.

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

It is not a de Polignac number, because 66810981 - 2¹⁰ = 66809957 is a prime.

It is a super-2 number, since 2×66810981² = 8927414364364722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66810181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 114505 + ... + 115086.

It is an arithmetic number, because the mean of its divisors is an integer number (11250008).

Almost surely, 2^66810981 is an apocalyptic number.

It is an amenable number.

66810981 is a deficient number, since it is larger than the sum of its proper divisors (23189083).

66810981 is a wasteful number, since it uses less digits than its factorization.

66810981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 229691.

The product of its (nonzero) digits is 20736, while the sum is 39.

The square root of 66810981 is about 8173.7984438081. The cubic root of 66810981 is about 405.7725051476.

Adding to 66810981 its sum of digits (39), we get a triangular number (66811020 = T₁₁₅₅₉).

The spelling of 66810981 in words is "sixty-six million, eight hundred ten thousand, nine hundred eighty-one".