21820459 has 2 divisors, whose sum is σ = 21820460. Its totient is φ = 21820458.

The previous prime is 21820457. The next prime is 21820481. The reversal of 21820459 is 95402812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21820459 - 2¹ = 21820457 is a prime.

It is a super-2 number, since 2×21820459² = 952264861941362, which contains 22 as substring.

Together with 21820457, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21820459.

It is not a weakly prime, because it can be changed into another prime (21820457) 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, 10910229 + 10910230.

It is an arithmetic number, because the mean of its divisors is an integer number (10910230).

Almost surely, 2^21820459 is an apocalyptic number.

21820459 is a deficient number, since it is larger than the sum of its proper divisors (1).

21820459 is an equidigital number, since it uses as much as digits as its factorization.

21820459 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 21820459 is about 4671.2374163598. The cubic root of 21820459 is about 279.4396062134.

The spelling of 21820459 in words is "twenty-one million, eight hundred twenty thousand, four hundred fifty-nine".