2166821 has 2 divisors, whose sum is σ = 2166822. Its totient is φ = 2166820.

The previous prime is 2166797. The next prime is 2166833. The reversal of 2166821 is 1286612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2070721 + 96100 = 1439^2 + 310^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2166821 is a prime.

It is a super-2 number, since 2×2166821² = 9390226492082, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2166121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1083410 + 1083411.

It is an arithmetic number, because the mean of its divisors is an integer number (1083411).

2^2166821 is an apocalyptic number.

It is an amenable number.

2166821 is a deficient number, since it is larger than the sum of its proper divisors (1).

2166821 is an equidigital number, since it uses as much as digits as its factorization.

2166821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 26.

The square root of 2166821 is about 1472.0125678811. The cubic root of 2166821 is about 129.4020069332.

The spelling of 2166821 in words is "two million, one hundred sixty-six thousand, eight hundred twenty-one".