7961721861 has 12 divisors (see below), whose sum is σ = 10736278112. Its totient is φ = 5248160544.

The previous prime is 7961721853. The next prime is 7961721863. The reversal of 7961721861 is 1681271697.

It is not a de Polignac number, because 7961721861 - 2³ = 7961721853 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 7961721861.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7961721863) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 143761 + ... + 191286.

Almost surely, 2^7961721861 is an apocalyptic number.

It is an amenable number.

7961721861 is a deficient number, since it is larger than the sum of its proper divisors (2774556251).

7961721861 is an equidigital number, since it uses as much as digits as its factorization.

7961721861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 335228 (or 335139 counting only the distinct ones).

The product of its digits is 254016, while the sum is 48.

The square root of 7961721861 is about 89228.4812209644. The cubic root of 7961721861 is about 1996.8050539610.

The spelling of 7961721861 in words is "seven billion, nine hundred sixty-one million, seven hundred twenty-one thousand, eight hundred sixty-one".