7971940721 has 4 divisors (see below), whose sum is σ = 7977296100. Its totient is φ = 7966585344.

The previous prime is 7971940661. The next prime is 7971940723. The reversal of 7971940721 is 1270491797.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2768338225 + 5203602496 = 52615^2 + 72136^2 .

It is a cyclic number.

It is not a de Polignac number, because 7971940721 - 2²² = 7967746417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7971940723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2675456 + ... + 2678433.

It is an arithmetic number, because the mean of its divisors is an integer number (1994324025).

Almost surely, 2^7971940721 is an apocalyptic number.

It is an amenable number.

7971940721 is a deficient number, since it is larger than the sum of its proper divisors (5355379).

7971940721 is a wasteful number, since it uses less digits than its factorization.

7971940721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5355378.

The product of its (nonzero) digits is 222264, while the sum is 47.

The square root of 7971940721 is about 89285.7251804565. The cubic root of 7971940721 is about 1997.6589876497.

The spelling of 7971940721 in words is "seven billion, nine hundred seventy-one million, nine hundred forty thousand, seven hundred twenty-one".