21505422031 has 4 divisors (see below), whose sum is σ = 21581954064. Its totient is φ = 21428890000.

The previous prime is 21505422019. The next prime is 21505422097. The reversal of 21505422031 is 13022450512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21505422031 is a prime.

It is a super-2 number, since 2×21505422031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21505421987 and 21505422005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505422011) 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 3 ways as a sum of consecutive naturals, for example, 38265595 + ... + 38266156.

It is an arithmetic number, because the mean of its divisors is an integer number (5395488516).

Almost surely, 2^21505422031 is an apocalyptic number.

21505422031 is a deficient number, since it is larger than the sum of its proper divisors (76532033).

21505422031 is an equidigital number, since it uses as much as digits as its factorization.

21505422031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76532032.

The product of its (nonzero) digits is 2400, while the sum is 25.

Adding to 21505422031 its reverse (13022450512), we get a palindrome (34527872543).

The spelling of 21505422031 in words is "twenty-one billion, five hundred five million, four hundred twenty-two thousand, thirty-one".