6815810661 has 16 divisors (see below), whose sum is σ = 10076432448. Its totient is φ = 4063075200.

The previous prime is 6815810543. The next prime is 6815810693. The reversal of 6815810661 is 1660185186.

It is a de Polignac number, because none of the positive numbers 2^k-6815810661 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6815810861) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1690936 + ... + 1694961.

It is an arithmetic number, because the mean of its divisors is an integer number (629777028).

Almost surely, 2^6815810661 is an apocalyptic number.

6815810661 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

6815810661 is a deficient number, since it is larger than the sum of its proper divisors (3260621787).

6815810661 is a wasteful number, since it uses less digits than its factorization.

6815810661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3385972.

The product of its (nonzero) digits is 69120, while the sum is 42.

The square root of 6815810661 is about 82557.9230661722. The cubic root of 6815810661 is about 1896.0036649927.

The spelling of 6815810661 in words is "six billion, eight hundred fifteen million, eight hundred ten thousand, six hundred sixty-one".