647639 has 4 divisors (see below), whose sum is σ = 652080. Its totient is φ = 643200.

The previous prime is 647627. The next prime is 647641. The reversal of 647639 is 936746.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-647639 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 647599 and 647608.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 647639.

It is not an unprimeable number, because it can be changed into a prime (647609) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1994 + ... + 2295.

It is an arithmetic number, because the mean of its divisors is an integer number (163020).

2⁶⁴⁷⁶³⁹ is an apocalyptic number.

647639 is a deficient number, since it is larger than the sum of its proper divisors (4441).

647639 is a wasteful number, since it uses less digits than its factorization.

647639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4440.

The product of its digits is 27216, while the sum is 35.

The square root of 647639 is about 804.7602127342. The cubic root of 647639 is about 86.5189017243.

The spelling of 647639 in words is "six hundred forty-seven thousand, six hundred thirty-nine".