7856636561 has 2 divisors, whose sum is σ = 7856636562. Its totient is φ = 7856636560.

The previous prime is 7856636549. The next prime is 7856636569. The reversal of 7856636561 is 1656366587.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6625960000 + 1230676561 = 81400^2 + 35081^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7856636561 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (7856636569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3928318280 + 3928318281.

It is an arithmetic number, because the mean of its divisors is an integer number (3928318281).

Almost surely, 2^7856636561 is an apocalyptic number.

It is an amenable number.

7856636561 is a deficient number, since it is larger than the sum of its proper divisors (1).

7856636561 is an equidigital number, since it uses as much as digits as its factorization.

7856636561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5443200, while the sum is 53.

The square root of 7856636561 is about 88637.6701013739. The cubic root of 7856636561 is about 1987.9809628089.

The spelling of 7856636561 in words is "seven billion, eight hundred fifty-six million, six hundred thirty-six thousand, five hundred sixty-one".