66557763662891 has 4 divisors (see below), whose sum is σ = 66728863312800. Its totient is φ = 66386664012984.

The previous prime is 66557763662879. The next prime is 66557763662963. The reversal of 66557763662891 is 19826636775566.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 66557763662891 - 2⁶ = 66557763662827 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66557763662861) 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, 85549824371 + ... + 85549825148.

It is an arithmetic number, because the mean of its divisors is an integer number (16682215828200).

Almost surely, 2^{66557763662891} is an apocalyptic number.

66557763662891 is a deficient number, since it is larger than the sum of its proper divisors (171099649909).

66557763662891 is a wasteful number, since it uses less digits than its factorization.

66557763662891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 171099649908.

The product of its digits is 4115059200, while the sum is 77.

The spelling of 66557763662891 in words is "sixty-six trillion, five hundred fifty-seven billion, seven hundred sixty-three million, six hundred sixty-two thousand, eight hundred ninety-one".