66800509 has 4 divisors (see below), whose sum is σ = 66865120. Its totient is φ = 66735900.

The previous prime is 66800507. The next prime is 66800527. The reversal of 66800509 is 90500866.

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, and also an emirpimes, since its reverse is a distinct semiprime: 90500866 = 2 ⋅45250433.

It is a cyclic number.

It is not a de Polignac number, because 66800509 - 2¹ = 66800507 is a prime.

It is a super-3 number, since 3×66800509³ (a number of 24 digits) contains 333 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 (66800507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 30729 + ... + 32830.

It is an arithmetic number, because the mean of its divisors is an integer number (16716280).

Almost surely, 2^66800509 is an apocalyptic number.

It is an amenable number.

66800509 is a deficient number, since it is larger than the sum of its proper divisors (64611).

66800509 is a wasteful number, since it uses less digits than its factorization.

66800509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64610.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 66800509 is about 8173.1578352556. The cubic root of 66800509 is about 405.7513036842.

The spelling of 66800509 in words is "sixty-six million, eight hundred thousand, five hundred nine".