21559423 has 2 divisors, whose sum is σ = 21559424. Its totient is φ = 21559422.

The previous prime is 21559409. The next prime is 21559427. The reversal of 21559423 is 32495512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21559423 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21559427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10779711 + 10779712.

It is an arithmetic number, because the mean of its divisors is an integer number (10779712).

Almost surely, 2^21559423 is an apocalyptic number.

21559423 is a deficient number, since it is larger than the sum of its proper divisors (1).

21559423 is an equidigital number, since it uses as much as digits as its factorization.

21559423 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10800, while the sum is 31.

The square root of 21559423 is about 4643.2125732083. The cubic root of 21559423 is about 278.3208301920.

The spelling of 21559423 in words is "twenty-one million, five hundred fifty-nine thousand, four hundred twenty-three".