2187120856721 has 2 divisors, whose sum is σ = 2187120856722. Its totient is φ = 2187120856720.

The previous prime is 2187120856681. The next prime is 2187120856787. The reversal of 2187120856721 is 1276580217812.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2184365761600 + 2755095121 = 1477960^2 + 52489^2 .

It is a cyclic number.

It is not a de Polignac number, because 2187120856721 - 2¹⁴ = 2187120840337 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2187120856721.

It is not a weakly prime, because it can be changed into another prime (2187120856321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1093560428360 + 1093560428361.

It is an arithmetic number, because the mean of its divisors is an integer number (1093560428361).

Almost surely, 2^{2187120856721} is an apocalyptic number.

It is an amenable number.

2187120856721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2187120856721 is an equidigital number, since it uses as much as digits as its factorization.

2187120856721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 752640, while the sum is 50.

The spelling of 2187120856721 in words is "two trillion, one hundred eighty-seven billion, one hundred twenty million, eight hundred fifty-six thousand, seven hundred twenty-one".