66604781 has 4 divisors (see below), whose sum is σ = 68021952. Its totient is φ = 65187612.

The previous prime is 66604763. The next prime is 66604801. The reversal of 66604781 is 18740666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66604781 - 2⁶ = 66604717 is a prime.

It is a super-2 number, since 2×66604781² = 8872393704115922, 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 (66604081) 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 3 ways as a sum of consecutive naturals, for example, 708515 + ... + 708608.

It is an arithmetic number, because the mean of its divisors is an integer number (17005488).

Almost surely, 2^66604781 is an apocalyptic number.

It is an amenable number.

66604781 is a deficient number, since it is larger than the sum of its proper divisors (1417171).

66604781 is a wasteful number, since it uses less digits than its factorization.

66604781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1417170.

The product of its (nonzero) digits is 48384, while the sum is 38.

The square root of 66604781 is about 8161.1752217435. The cubic root of 66604781 is about 405.3546271534.

The spelling of 66604781 in words is "sixty-six million, six hundred four thousand, seven hundred eighty-one".