21388865518 has 4 divisors (see below), whose sum is σ = 32083298280. Its totient is φ = 10694432758.

The previous prime is 21388865501. The next prime is 21388865521. The reversal of 21388865518 is 81556888312.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5347216378 + ... + 5347216381.

It is an arithmetic number, because the mean of its divisors is an integer number (8020824570).

Almost surely, 2^21388865518 is an apocalyptic number.

21388865518 is a deficient number, since it is larger than the sum of its proper divisors (10694432762).

21388865518 is a wasteful number, since it uses less digits than its factorization.

21388865518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10694432761.

The product of its digits is 3686400, while the sum is 55.

The spelling of 21388865518 in words is "twenty-one billion, three hundred eighty-eight million, eight hundred sixty-five thousand, five hundred eighteen".