66780981 has 12 divisors (see below), whose sum is σ = 102135852. Its totient is φ = 41901696.

The previous prime is 66780971. The next prime is 66781009. The reversal of 66780981 is 18908766.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 27468081 + 39312900 = 5241^2 + 6270^2 .

It is not a de Polignac number, because 66780981 - 2⁵ = 66780949 is a prime.

It is a super-2 number, since 2×66780981² = 8919398846644722, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66780971) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 218086 + ... + 218391.

It is an arithmetic number, because the mean of its divisors is an integer number (8511321).

Almost surely, 2^66780981 is an apocalyptic number.

It is an amenable number.

66780981 is a deficient number, since it is larger than the sum of its proper divisors (35354871).

66780981 is a wasteful number, since it uses less digits than its factorization.

66780981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 436500 (or 436497 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The square root of 66780981 is about 8171.9631056436. The cubic root of 66780981 is about 405.7117616517.

The spelling of 66780981 in words is "sixty-six million, seven hundred eighty thousand, nine hundred eighty-one".