66665551 has 4 divisors (see below), whose sum is σ = 70587072. Its totient is φ = 62744032.

The previous prime is 66665537. The next prime is 66665567. The reversal of 66665551 is 15556666.

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 66665551 - 2¹³ = 66657359 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66665591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1960735 + ... + 1960768.

It is an arithmetic number, because the mean of its divisors is an integer number (17646768).

Almost surely, 2^66665551 is an apocalyptic number.

66665551 is a deficient number, since it is larger than the sum of its proper divisors (3921521).

66665551 is a wasteful number, since it uses less digits than its factorization.

66665551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3921520.

The product of its digits is 162000, while the sum is 40.

The square root of 66665551 is about 8164.8974886400. The cubic root of 66665551 is about 405.4778711223.

The spelling of 66665551 in words is "sixty-six million, six hundred sixty-five thousand, five hundred fifty-one".