20356421 has 2 divisors, whose sum is σ = 20356422. Its totient is φ = 20356420.

The previous prime is 20356397. The next prime is 20356433. The reversal of 20356421 is 12465302.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11296321 + 9060100 = 3361^2 + 3010^2 .

It is a cyclic number.

It is not a de Polignac number, because 20356421 - 2¹⁴ = 20340037 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20352421) 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, 10178210 + 10178211.

It is an arithmetic number, because the mean of its divisors is an integer number (10178211).

Almost surely, 2^20356421 is an apocalyptic number.

It is an amenable number.

20356421 is a deficient number, since it is larger than the sum of its proper divisors (1).

20356421 is an equidigital number, since it uses as much as digits as its factorization.

20356421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 20356421 is about 4511.8090606762. The cubic root of 20356421 is about 273.0447358784.

The spelling of 20356421 in words is "twenty million, three hundred fifty-six thousand, four hundred twenty-one".