20278021 has 2 divisors, whose sum is σ = 20278022. Its totient is φ = 20278020.

The previous prime is 20278003. The next prime is 20278031. The reversal of 20278021 is 12087202.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19448100 + 829921 = 4410^2 + 911^2 .

It is a cyclic number.

It is not a de Polignac number, because 20278021 - 2⁷ = 20277893 is a prime.

It is a super-2 number, since 2×20278021² = 822396271352882, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20277983 and 20278001.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20278001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10139010 + 10139011.

It is an arithmetic number, because the mean of its divisors is an integer number (10139011).

Almost surely, 2^20278021 is an apocalyptic number.

It is an amenable number.

20278021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20278021 is an equidigital number, since it uses as much as digits as its factorization.

20278021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 20278021 is about 4503.1123681294. The cubic root of 20278021 is about 272.6937532913.

The spelling of 20278021 in words is "twenty million, two hundred seventy-eight thousand, twenty-one".