6461665821 has 36 divisors (see below), whose sum is σ = 10123958208. Its totient is φ = 3969624672.

The previous prime is 6461665817. The next prime is 6461665853. The reversal of 6461665821 is 1285661646.

6461665821 is a `hidden beast` number, since 6 + 4 + 6 + 1 + 66 + 582 + 1 = 666.

It is not a de Polignac number, because 6461665821 - 2² = 6461665817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6461665811) 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 35 ways as a sum of consecutive naturals, for example, 974700 + ... + 981306.

Almost surely, 2^6461665821 is an apocalyptic number.

It is an amenable number.

6461665821 is a deficient number, since it is larger than the sum of its proper divisors (3662292387).

6461665821 is a wasteful number, since it uses less digits than its factorization.

6461665821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7282 (or 7266 counting only the distinct ones).

The product of its digits is 414720, while the sum is 45.

The square root of 6461665821 is about 80384.4874400528. The cubic root of 6461665821 is about 1862.5795538951.

The spelling of 6461665821 in words is "six billion, four hundred sixty-one million, six hundred sixty-five thousand, eight hundred twenty-one".