21087559 has 4 divisors (see below), whose sum is σ = 21097440. Its totient is φ = 21077680.

The previous prime is 21087557. The next prime is 21087569. The reversal of 21087559 is 95578012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21087559 - 2¹ = 21087557 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21087557) 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 in 3 ways as a sum of consecutive naturals, for example, 262 + ... + 6499.

It is an arithmetic number, because the mean of its divisors is an integer number (5274360).

Almost surely, 2^21087559 is an apocalyptic number.

21087559 is a deficient number, since it is larger than the sum of its proper divisors (9881).

21087559 is an equidigital number, since it uses as much as digits as its factorization.

21087559 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9880.

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

The square root of 21087559 is about 4592.1192275463. The cubic root of 21087559 is about 276.2753282401.

The spelling of 21087559 in words is "twenty-one million, eighty-seven thousand, five hundred fifty-nine".