21856254815 has 8 divisors (see below), whose sum is σ = 26229037248. Its totient is φ = 17483982880.

The previous prime is 21856254779. The next prime is 21856254829. The reversal of 21856254815 is 51845265812.

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

It is not a de Polignac number, because 21856254815 - 2¹⁶ = 21856189279 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21856254815.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26087 + ... + 210696.

It is an arithmetic number, because the mean of its divisors is an integer number (3278629656).

Almost surely, 2^21856254815 is an apocalyptic number.

21856254815 is a deficient number, since it is larger than the sum of its proper divisors (4372782433).

21856254815 is a wasteful number, since it uses less digits than its factorization.

21856254815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255249.

The product of its digits is 768000, while the sum is 47.

The spelling of 21856254815 in words is "twenty-one billion, eight hundred fifty-six million, two hundred fifty-four thousand, eight hundred fifteen".