21423559 has 2 divisors, whose sum is σ = 21423560. Its totient is φ = 21423558.

The previous prime is 21423539. The next prime is 21423581. The reversal of 21423559 is 95532412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21423559 - 2⁵ = 21423527 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21423559.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21423509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10711779 + 10711780.

It is an arithmetic number, because the mean of its divisors is an integer number (10711780).

Almost surely, 2^21423559 is an apocalyptic number.

21423559 is a deficient number, since it is larger than the sum of its proper divisors (1).

21423559 is an equidigital number, since it uses as much as digits as its factorization.

21423559 is an evil number, because the sum of its binary digits is even.

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

The square root of 21423559 is about 4628.5590630346. The cubic root of 21423559 is about 277.7349534634.

The spelling of 21423559 in words is "twenty-one million, four hundred twenty-three thousand, five hundred fifty-nine".