7981285721 has 8 divisors (see below), whose sum is σ = 8263459080. Its totient is φ = 7699576192.

The previous prime is 7981285717. The next prime is 7981285751. The reversal of 7981285721 is 1275821897.

It can be written as a sum of positive squares in 4 ways, for example, as 3362724121 + 4618561600 = 57989^2 + 67960^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 7981285721 - 2² = 7981285717 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 7981285721.

It is not an unprimeable number, because it can be changed into a prime (7981285751) 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, 80750 + ... + 149943.

It is an arithmetic number, because the mean of its divisors is an integer number (1032932385).

Almost surely, 2^7981285721 is an apocalyptic number.

It is an amenable number.

7981285721 is a deficient number, since it is larger than the sum of its proper divisors (282173359).

7981285721 is a wasteful number, since it uses less digits than its factorization.

7981285721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 231915.

The product of its digits is 564480, while the sum is 50.

The square root of 7981285721 is about 89338.0418466848. The cubic root of 7981285721 is about 1998.4392591108.

The spelling of 7981285721 in words is "seven billion, nine hundred eighty-one million, two hundred eighty-five thousand, seven hundred twenty-one".