21003242431 has 4 divisors (see below), whose sum is σ = 21727492200. Its totient is φ = 20278992664.

The previous prime is 21003242423. The next prime is 21003242461. The reversal of 21003242431 is 13424230012.

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 21003242431 - 2³ = 21003242423 is a prime.

It is a super-2 number, since 2×21003242431² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003242401) 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, 362124841 + ... + 362124898.

It is an arithmetic number, because the mean of its divisors is an integer number (5431873050).

Almost surely, 2^21003242431 is an apocalyptic number.

21003242431 is a deficient number, since it is larger than the sum of its proper divisors (724249769).

21003242431 is an equidigital number, since it uses as much as digits as its factorization.

21003242431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724249768.

The product of its (nonzero) digits is 1152, while the sum is 22.

Adding to 21003242431 its reverse (13424230012), we get a palindrome (34427472443).

The spelling of 21003242431 in words is "twenty-one billion, three million, two hundred forty-two thousand, four hundred thirty-one".