398821 has 2 divisors, whose sum is σ = 398822. Its totient is φ = 398820.

The previous prime is 398819. The next prime is 398833. The reversal of 398821 is 128893.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 314721 + 84100 = 561^2 + 290^2 .

It is a cyclic number.

It is not a de Polignac number, because 398821 - 2¹ = 398819 is a prime.

Together with 398819, 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 (398621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199410 + 199411.

It is an arithmetic number, because the mean of its divisors is an integer number (199411).

2³⁹⁸⁸²¹ is an apocalyptic number.

It is an amenable number.

398821 is a deficient number, since it is larger than the sum of its proper divisors (1).

398821 is an equidigital number, since it uses as much as digits as its factorization.

398821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456, while the sum is 31.

The square root of 398821 is about 631.5227628518. The cubic root of 398821 is about 73.6081675128.

The spelling of 398821 in words is "three hundred ninety-eight thousand, eight hundred twenty-one".