21391586 has 8 divisors (see below), whose sum is σ = 32870124. Its totient is φ = 10434880.

The previous prime is 21391583. The next prime is 21391603. The reversal of 21391586 is 68519312.

It can be written as a sum of positive squares in 2 ways, for example, as 21390625 + 961 = 4625^2 + 31^2 .

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21391583) 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, 130355 + ... + 130518.

Almost surely, 2^21391586 is an apocalyptic number.

21391586 is a deficient number, since it is larger than the sum of its proper divisors (11478538).

21391586 is a wasteful number, since it uses less digits than its factorization.

21391586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 260916.

The product of its digits is 12960, while the sum is 35.

The square root of 21391586 is about 4625.1038907251. The cubic root of 21391586 is about 277.5967187142.

The spelling of 21391586 in words is "twenty-one million, three hundred ninety-one thousand, five hundred eighty-six".