21171855239 has 4 divisors (see below), whose sum is σ = 21173107824. Its totient is φ = 21170602656.

The previous prime is 21171855209. The next prime is 21171855241. The reversal of 21171855239 is 93255817112.

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 21171855239 - 2²⁸ = 20903419783 is a prime.

It is a super-2 number, since 2×21171855239² (a number of 21 digits) contains 22 as substring.

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 21171855239.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21171855209) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 600587 + ... + 634860.

It is an arithmetic number, because the mean of its divisors is an integer number (5293276956).

Almost surely, 2^21171855239 is an apocalyptic number.

21171855239 is a deficient number, since it is larger than the sum of its proper divisors (1252585).

21171855239 is a wasteful number, since it uses less digits than its factorization.

21171855239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1252584.

The product of its digits is 151200, while the sum is 44.

The spelling of 21171855239 in words is "twenty-one billion, one hundred seventy-one million, eight hundred fifty-five thousand, two hundred thirty-nine".