66763991 has 4 divisors (see below), whose sum is σ = 76301712. Its totient is φ = 57226272.

The previous prime is 66763979. The next prime is 66763999. The reversal of 66763991 is 19936766.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66763991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66763999) 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, 4768850 + ... + 4768863.

It is an arithmetic number, because the mean of its divisors is an integer number (19075428).

Almost surely, 2^66763991 is an apocalyptic number.

66763991 is a deficient number, since it is larger than the sum of its proper divisors (9537721).

66763991 is an equidigital number, since it uses as much as digits as its factorization.

66763991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9537720.

The product of its digits is 367416, while the sum is 47.

The square root of 66763991 is about 8170.9235096163. The cubic root of 66763991 is about 405.6773525162.

The spelling of 66763991 in words is "sixty-six million, seven hundred sixty-three thousand, nine hundred ninety-one".