646779209 has 8 divisors (see below), whose sum is σ = 681222240. Its totient is φ = 612376416.

The previous prime is 646779187. The next prime is 646779233. The reversal of 646779209 is 902977646.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646779209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646779239) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26357 + ... + 44589.

It is an arithmetic number, because the mean of its divisors is an integer number (85152780).

Almost surely, 2^646779209 is an apocalyptic number.

It is an amenable number.

646779209 is a deficient number, since it is larger than the sum of its proper divisors (34443031).

646779209 is a wasteful number, since it uses less digits than its factorization.

646779209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20119.

The product of its (nonzero) digits is 1143072, while the sum is 50.

The square root of 646779209 is about 25431.8542186762. The cubic root of 646779209 is about 864.8059791823.

The spelling of 646779209 in words is "six hundred forty-six million, seven hundred seventy-nine thousand, two hundred nine".