2129821 has 2 divisors, whose sum is σ = 2129822. Its totient is φ = 2129820.

The previous prime is 2129819. The next prime is 2129837. The reversal of 2129821 is 1289212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1726596 + 403225 = 1314^2 + 635^2 .

It is a cyclic number.

It is not a de Polignac number, because 2129821 - 2¹ = 2129819 is a prime.

It is a super-2 number, since 2×2129821² = 9072274984082, which contains 22 as substring.

Together with 2129819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2129851) 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, 1064910 + 1064911.

It is an arithmetic number, because the mean of its divisors is an integer number (1064911).

2^2129821 is an apocalyptic number.

It is an amenable number.

2129821 is a deficient number, since it is larger than the sum of its proper divisors (1).

2129821 is an equidigital number, since it uses as much as digits as its factorization.

2129821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 576, while the sum is 25.

The square root of 2129821 is about 1459.3906262547. The cubic root of 2129821 is about 128.6612307952.

The spelling of 2129821 in words is "two million, one hundred twenty-nine thousand, eight hundred twenty-one".