21205040124 has 24 divisors (see below), whose sum is σ = 50629089280. Its totient is φ = 6903966384.

The previous prime is 21205040123. The next prime is 21205040137. The reversal of 21205040124 is 42104050212.

It is a self number, because there is not a number n which added to its sum of digits gives 21205040124.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21205040123) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20547004 + ... + 20548035.

Almost surely, 2^21205040124 is an apocalyptic number.

It is an amenable number.

21205040124 is an abundant number, since it is smaller than the sum of its proper divisors (29424049156).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21205040124 is a wasteful number, since it uses less digits than its factorization.

21205040124 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41095089 (or 41095087 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 21.

Adding to 21205040124 its reverse (42104050212), we get a palindrome (63309090336).

The spelling of 21205040124 in words is "twenty-one billion, two hundred five million, forty thousand, one hundred twenty-four".