21538586 has 4 divisors (see below), whose sum is σ = 32307882. Its totient is φ = 10769292.

The previous prime is 21538579. The next prime is 21538589. The reversal of 21538586 is 68583512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 20475625 + 1062961 = 4525^2 + 1031^2 .

It is not an unprimeable number, because it can be changed into a prime (21538589) 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, 5384645 + ... + 5384648.

Almost surely, 2^21538586 is an apocalyptic number.

21538586 is a deficient number, since it is larger than the sum of its proper divisors (10769296).

21538586 is a wasteful number, since it uses less digits than its factorization.

21538586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10769295.

The product of its digits is 57600, while the sum is 38.

The square root of 21538586 is about 4640.9682179476. The cubic root of 21538586 is about 278.2311363802.

The spelling of 21538586 in words is "twenty-one million, five hundred thirty-eight thousand, five hundred eighty-six".