2156771866861 has 2 divisors, whose sum is σ = 2156771866862. Its totient is φ = 2156771866860.

The previous prime is 2156771866841. The next prime is 2156771866867. The reversal of 2156771866861 is 1686681776512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1218186801225 + 938585065636 = 1103715^2 + 968806^2 .

It is a cyclic number.

It is not a de Polignac number, because 2156771866861 - 2⁵ = 2156771866829 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 2156771866793 and 2156771866802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2156771866867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1078385933430 + 1078385933431.

It is an arithmetic number, because the mean of its divisors is an integer number (1078385933431).

Almost surely, 2^{2156771866861} is an apocalyptic number.

It is an amenable number.

2156771866861 is a deficient number, since it is larger than the sum of its proper divisors (1).

2156771866861 is an equidigital number, since it uses as much as digits as its factorization.

2156771866861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40642560, while the sum is 64.

The spelling of 2156771866861 in words is "two trillion, one hundred fifty-six billion, seven hundred seventy-one million, eight hundred sixty-six thousand, eight hundred sixty-one".