66987571 has 4 divisors (see below), whose sum is σ = 76557232. Its totient is φ = 57417912.

The previous prime is 66987551. The next prime is 66987611. The reversal of 66987571 is 17578966.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17578966 = 2 ⋅8789483.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66987571 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66987511) 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, 4784820 + ... + 4784833.

It is an arithmetic number, because the mean of its divisors is an integer number (19139308).

Almost surely, 2^66987571 is an apocalyptic number.

66987571 is a deficient number, since it is larger than the sum of its proper divisors (9569661).

66987571 is an equidigital number, since it uses as much as digits as its factorization.

66987571 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9569660.

The product of its digits is 635040, while the sum is 49.

The square root of 66987571 is about 8184.5935146469. The cubic root of 66987571 is about 406.1296935753.

The spelling of 66987571 in words is "sixty-six million, nine hundred eighty-seven thousand, five hundred seventy-one".