666635645 has 16 divisors (see below), whose sum is σ = 862221360. Its totient is φ = 491871744.

The previous prime is 666635621. The next prime is 666635663. The reversal of 666635645 is 546536666.

It can be written as a sum of positive squares in 8 ways, for example, as 45778756 + 620856889 = 6766^2 + 24917^2 .

It is not a de Polignac number, because 666635645 - 2¹⁶ = 666570109 is a prime.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 666635645.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 89297 + ... + 96473.

It is an arithmetic number, because the mean of its divisors is an integer number (53888835).

Almost surely, 2^666635645 is an apocalyptic number.

666635645 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

666635645 is a deficient number, since it is larger than the sum of its proper divisors (195585715).

666635645 is a wasteful number, since it uses less digits than its factorization.

666635645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8624.

The product of its digits is 2332800, while the sum is 47.

The square root of 666635645 is about 25819.2882357357. The cubic root of 666635645 is about 873.5669145651.

The spelling of 666635645 in words is "six hundred sixty-six million, six hundred thirty-five thousand, six hundred forty-five".