21520404231 has 8 divisors (see below), whose sum is σ = 29361171840. Its totient is φ = 14013286392.

The previous prime is 21520404229. The next prime is 21520404233. The reversal of 21520404231 is 13240402512.

It is an interprime number because it is at equal distance from previous prime (21520404229) and next prime (21520404233).

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

It is not a de Polignac number, because 21520404231 - 2¹ = 21520404229 is a prime.

It is a super-2 number, since 2×21520404231² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520404233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 83412291 + ... + 83412548.

It is an arithmetic number, because the mean of its divisors is an integer number (3670146480).

Almost surely, 2^21520404231 is an apocalyptic number.

21520404231 is a deficient number, since it is larger than the sum of its proper divisors (7840767609).

21520404231 is a wasteful number, since it uses less digits than its factorization.

21520404231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166824885.

The product of its (nonzero) digits is 1920, while the sum is 24.

Adding to 21520404231 its reverse (13240402512), we get a palindrome (34760806743).

The spelling of 21520404231 in words is "twenty-one billion, five hundred twenty million, four hundred four thousand, two hundred thirty-one".