639445769 has 4 divisors (see below), whose sum is σ = 677060244. Its totient is φ = 601831296.

The previous prime is 639445759. The next prime is 639445777. The reversal of 639445769 is 967544936.

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

It can be written as a sum of positive squares in 2 ways, for example, as 194742025 + 444703744 = 13955^2 + 21088^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639445769 is a prime.

It is a super-2 number, since 2×639445769² = 817781782984002722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639445769.

It is not an unprimeable number, because it can be changed into a prime (639445739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18807212 + ... + 18807245.

It is an arithmetic number, because the mean of its divisors is an integer number (169265061).

Almost surely, 2^639445769 is an apocalyptic number.

It is an amenable number.

639445769 is a deficient number, since it is larger than the sum of its proper divisors (37614475).

639445769 is a wasteful number, since it uses less digits than its factorization.

639445769 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37614474.

The product of its digits is 4898880, while the sum is 53.

The square root of 639445769 is about 25287.2649568908. The cubic root of 639445769 is about 861.5250428176.

The spelling of 639445769 in words is "six hundred thirty-nine million, four hundred forty-five thousand, seven hundred sixty-nine".