20421859 has 2 divisors, whose sum is σ = 20421860. Its totient is φ = 20421858.

The previous prime is 20421803. The next prime is 20421871. The reversal of 20421859 is 95812402.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20421859 - 2⁹ = 20421347 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20421859.

It is not a weakly prime, because it can be changed into another prime (20421899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10210929 + 10210930.

It is an arithmetic number, because the mean of its divisors is an integer number (10210930).

Almost surely, 2^20421859 is an apocalyptic number.

20421859 is a deficient number, since it is larger than the sum of its proper divisors (1).

20421859 is an equidigital number, since it uses as much as digits as its factorization.

20421859 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 20421859 is about 4519.0551003501. The cubic root of 20421859 is about 273.3370005787.

The spelling of 20421859 in words is "twenty million, four hundred twenty-one thousand, eight hundred fifty-nine".