7856540221 has 2 divisors, whose sum is σ = 7856540222. Its totient is φ = 7856540220.

The previous prime is 7856540203. The next prime is 7856540231. The reversal of 7856540221 is 1220456587.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7856163225 + 376996 = 88635^2 + 614^2 .

It is a cyclic number.

It is not a de Polignac number, because 7856540221 - 2²⁵ = 7822985789 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7856540231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3928270110 + 3928270111.

It is an arithmetic number, because the mean of its divisors is an integer number (3928270111).

Almost surely, 2^7856540221 is an apocalyptic number.

It is an amenable number.

7856540221 is a deficient number, since it is larger than the sum of its proper divisors (1).

7856540221 is an equidigital number, since it uses as much as digits as its factorization.

7856540221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 134400, while the sum is 40.

The square root of 7856540221 is about 88637.1266513079. The cubic root of 7856540221 is about 1987.9728370727.

The spelling of 7856540221 in words is "seven billion, eight hundred fifty-six million, five hundred forty thousand, two hundred twenty-one".