66135781 has 4 divisors (see below), whose sum is σ = 66204864. Its totient is φ = 66066700.

The previous prime is 66135749. The next prime is 66135793. The reversal of 66135781 is 18753166.

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 66135781 - 2⁵ = 66135749 is a prime.

It is a super-2 number, since 2×66135781² = 8747883056959922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66135781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66135701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33085 + ... + 35026.

It is an arithmetic number, because the mean of its divisors is an integer number (16551216).

Almost surely, 2^66135781 is an apocalyptic number.

It is an amenable number.

66135781 is a deficient number, since it is larger than the sum of its proper divisors (69083).

66135781 is an equidigital number, since it uses as much as digits as its factorization.

66135781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69082.

The product of its digits is 30240, while the sum is 37.

The square root of 66135781 is about 8132.3908538633. The cubic root of 66135781 is about 404.4009453686.

The spelling of 66135781 in words is "sixty-six million, one hundred thirty-five thousand, seven hundred eighty-one".