66312781 has 4 divisors (see below), whose sum is σ = 67302592. Its totient is φ = 65322972.

The previous prime is 66312773. The next prime is 66312787. The reversal of 66312781 is 18721366.

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 66312781 - 2³ = 66312773 is a prime.

It is a super-2 number, since 2×66312781² = 8794769847907922, 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 (66312787) 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, 494805 + ... + 494938.

It is an arithmetic number, because the mean of its divisors is an integer number (16825648).

Almost surely, 2^66312781 is an apocalyptic number.

It is an amenable number.

66312781 is a deficient number, since it is larger than the sum of its proper divisors (989811).

66312781 is an equidigital number, since it uses as much as digits as its factorization.

66312781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 989810.

The product of its digits is 12096, while the sum is 34.

The square root of 66312781 is about 8143.2659909891. The cubic root of 66312781 is about 404.7613917368.

The spelling of 66312781 in words is "sixty-six million, three hundred twelve thousand, seven hundred eighty-one".