21243521431 has 4 divisors (see below), whose sum is σ = 23174750664. Its totient is φ = 19312292200.

The previous prime is 21243521363. The next prime is 21243521449. The reversal of 21243521431 is 13412534212.

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 21243521431 - 2¹⁷ = 21243390359 is a prime.

It is a super-2 number, since 2×21243521431² (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 21243521431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243528431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 965614600 + ... + 965614621.

It is an arithmetic number, because the mean of its divisors is an integer number (5793687666).

Almost surely, 2^21243521431 is an apocalyptic number.

21243521431 is a deficient number, since it is larger than the sum of its proper divisors (1931229233).

21243521431 is a wasteful number, since it uses less digits than its factorization.

21243521431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1931229232.

The product of its digits is 5760, while the sum is 28.

The spelling of 21243521431 in words is "twenty-one billion, two hundred forty-three million, five hundred twenty-one thousand, four hundred thirty-one".