21208611539 has 4 divisors (see below), whose sum is σ = 21219912624. Its totient is φ = 21197310456.

The previous prime is 21208611517. The next prime is 21208611563. The reversal of 21208611539 is 93511680212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21208611539 - 2⁸ = 21208611283 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21208611139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5647727 + ... + 5651480.

It is an arithmetic number, because the mean of its divisors is an integer number (5304978156).

Almost surely, 2^21208611539 is an apocalyptic number.

21208611539 is a deficient number, since it is larger than the sum of its proper divisors (11301085).

21208611539 is a wasteful number, since it uses less digits than its factorization.

21208611539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11301084.

The product of its (nonzero) digits is 25920, while the sum is 38.

The spelling of 21208611539 in words is "twenty-one billion, two hundred eight million, six hundred eleven thousand, five hundred thirty-nine".