7856867981 has 2 divisors, whose sum is σ = 7856867982. Its totient is φ = 7856867980.

The previous prime is 7856867969. The next prime is 7856867989. The reversal of 7856867981 is 1897686587.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4848893956 + 3007974025 = 69634^2 + 54845^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7856867981 is a prime.

It is a super-2 number, since 2×7856867981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7856867989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3928433990 + 3928433991.

It is an arithmetic number, because the mean of its divisors is an integer number (3928433991).

Almost surely, 2^7856867981 is an apocalyptic number.

It is an amenable number.

7856867981 is a deficient number, since it is larger than the sum of its proper divisors (1).

7856867981 is an equidigital number, since it uses as much as digits as its factorization.

7856867981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40642560, while the sum is 65.

The square root of 7856867981 is about 88638.9755186735. The cubic root of 7856867981 is about 1988.0004815107. Note that the first 3 decimals are identical.

The spelling of 7856867981 in words is "seven billion, eight hundred fifty-six million, eight hundred sixty-seven thousand, nine hundred eighty-one".