21087566 has 8 divisors (see below), whose sum is σ = 31795824. Its totient is φ = 10488960.

The previous prime is 21087557. The next prime is 21087569. The reversal of 21087566 is 66578012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21087569) 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, 26930 + ... + 27701.

It is an arithmetic number, because the mean of its divisors is an integer number (3974478).

Almost surely, 2^21087566 is an apocalyptic number.

21087566 is a deficient number, since it is larger than the sum of its proper divisors (10708258).

21087566 is a wasteful number, since it uses less digits than its factorization.

21087566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54826.

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 21087566 is about 4592.1199897215. The cubic root of 21087566 is about 276.2753588099.

The spelling of 21087566 in words is "twenty-one million, eighty-seven thousand, five hundred sixty-six".