66641561551 has 4 divisors (see below), whose sum is σ = 68191365352. Its totient is φ = 65091757752.

The previous prime is 66641561537. The next prime is 66641561573. The reversal of 66641561551 is 15516514666.

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 66641561551 - 2¹³ = 66641553359 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 (66641561851) 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, 774901836 + ... + 774901921.

It is an arithmetic number, because the mean of its divisors is an integer number (17047841338).

Almost surely, 2^66641561551 is an apocalyptic number.

66641561551 is a deficient number, since it is larger than the sum of its proper divisors (1549803801).

66641561551 is a wasteful number, since it uses less digits than its factorization.

66641561551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1549803800.

The product of its digits is 648000, while the sum is 46.

The spelling of 66641561551 in words is "sixty-six billion, six hundred forty-one million, five hundred sixty-one thousand, five hundred fifty-one".