21078559 has 2 divisors, whose sum is σ = 21078560. Its totient is φ = 21078558.

The previous prime is 21078527. The next prime is 21078587. The reversal of 21078559 is 95587012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21078559 - 2⁵ = 21078527 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21078509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10539279 + 10539280.

It is an arithmetic number, because the mean of its divisors is an integer number (10539280).

Almost surely, 2^21078559 is an apocalyptic number.

21078559 is a deficient number, since it is larger than the sum of its proper divisors (1).

21078559 is an equidigital number, since it uses as much as digits as its factorization.

21078559 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 21078559 is about 4591.1391832529. The cubic root of 21078559 is about 276.2360186204.

The spelling of 21078559 in words is "twenty-one million, seventy-eight thousand, five hundred fifty-nine".