20398891 has 2 divisors, whose sum is σ = 20398892. Its totient is φ = 20398890.

The previous prime is 20398871. The next prime is 20398897. The reversal of 20398891 is 19889302.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20398891 - 2¹⁵ = 20366123 is a prime.

It is a super-2 number, since 2×20398891² = 832229508059762, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20398897) 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, 10199445 + 10199446.

It is an arithmetic number, because the mean of its divisors is an integer number (10199446).

Almost surely, 2^20398891 is an apocalyptic number.

20398891 is a deficient number, since it is larger than the sum of its proper divisors (1).

20398891 is an equidigital number, since it uses as much as digits as its factorization.

20398891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 20398891 is about 4516.5131462224. The cubic root of 20398891 is about 273.2344901710.

The spelling of 20398891 in words is "twenty million, three hundred ninety-eight thousand, eight hundred ninety-one".