666639551 has 4 divisors (see below), whose sum is σ = 666752352. Its totient is φ = 666526752.

The previous prime is 666639539. The next prime is 666639553. The reversal of 666639551 is 155936666.

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 666639551 - 2⁶ = 666639487 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 666639496 and 666639505.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666639553) 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, 47015 + ... + 59528.

It is an arithmetic number, because the mean of its divisors is an integer number (166688088).

Almost surely, 2^666639551 is an apocalyptic number.

666639551 is a deficient number, since it is larger than the sum of its proper divisors (112801).

666639551 is a wasteful number, since it uses less digits than its factorization.

666639551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 112800.

The product of its digits is 874800, while the sum is 47.

The square root of 666639551 is about 25819.3638767496. The cubic root of 666639551 is about 873.5686207174.

The spelling of 666639551 in words is "six hundred sixty-six million, six hundred thirty-nine thousand, five hundred fifty-one".