641856517 has 8 divisors (see below), whose sum is σ = 660343320. Its totient is φ = 623504640.

The previous prime is 641856503. The next prime is 641856521. The reversal of 641856517 is 715658146.

It can be written as a sum of positive squares in 4 ways, for example, as 38613796 + 603242721 = 6214^2 + 24561^2 .

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-641856517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641856557) 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, 24042 + ... + 43147.

It is an arithmetic number, because the mean of its divisors is an integer number (82542915).

Almost surely, 2^641856517 is an apocalyptic number.

It is an amenable number.

641856517 is a deficient number, since it is larger than the sum of its proper divisors (18486803).

641856517 is a wasteful number, since it uses less digits than its factorization.

641856517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67463.

The product of its digits is 201600, while the sum is 43.

The square root of 641856517 is about 25334.8873492660. The cubic root of 641856517 is about 862.6063517109.

It can be divided in two parts, 64 and 1856517, that added together give a palindrome (1856581).

The spelling of 641856517 in words is "six hundred forty-one million, eight hundred fifty-six thousand, five hundred seventeen".