2156643221 has 2 divisors, whose sum is σ = 2156643222. Its totient is φ = 2156643220.

The previous prime is 2156643211. The next prime is 2156643233. The reversal of 2156643221 is 1223466512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2156580721 + 62500 = 46439^2 + 250^2 .

It is a cyclic number.

It is not a de Polignac number, because 2156643221 - 2²⁶ = 2089534357 is a prime.

It is a super-2 number, since 2×2156643221² = 9302219965370509682, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2156643211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1078321610 + 1078321611.

It is an arithmetic number, because the mean of its divisors is an integer number (1078321611).

Almost surely, 2^2156643221 is an apocalyptic number.

It is an amenable number.

2156643221 is a deficient number, since it is larger than the sum of its proper divisors (1).

2156643221 is an equidigital number, since it uses as much as digits as its factorization.

2156643221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17280, while the sum is 32.

The square root of 2156643221 is about 46439.6729208981. The cubic root of 2156643221 is about 1291.9908408087.

The spelling of 2156643221 in words is "two billion, one hundred fifty-six million, six hundred forty-three thousand, two hundred twenty-one".