21559831939 has 4 divisors (see below), whose sum is σ = 21561702624. Its totient is φ = 21557961256.

The previous prime is 21559831933. The next prime is 21559831961. The reversal of 21559831939 is 93913895512.

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 21559831939 - 2²¹ = 21557734787 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 21559831939.

It is not an unprimeable number, because it can be changed into a prime (21559831933) 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, 917947 + ... + 941140.

It is an arithmetic number, because the mean of its divisors is an integer number (5390425656).

Almost surely, 2^21559831939 is an apocalyptic number.

21559831939 is a deficient number, since it is larger than the sum of its proper divisors (1870685).

21559831939 is a wasteful number, since it uses less digits than its factorization.

21559831939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1870684.

The product of its digits is 2624400, while the sum is 55.

The spelling of 21559831939 in words is "twenty-one billion, five hundred fifty-nine million, eight hundred thirty-one thousand, nine hundred thirty-nine".