21000431243 has 6 divisors (see below), whose sum is σ = 23083118772. Its totient is φ = 19091301020.

The previous prime is 21000431213. The next prime is 21000431261. The reversal of 21000431243 is 34213400012.

It is not a de Polignac number, because 21000431243 - 2⁸ = 21000430987 is a prime.

It is a super-2 number, since 2×21000431243² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21000431213) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 86778521 + ... + 86778762.

It is an arithmetic number, because the mean of its divisors is an integer number (3847186462).

Almost surely, 2^21000431243 is an apocalyptic number.

21000431243 is a deficient number, since it is larger than the sum of its proper divisors (2082687529).

21000431243 is a wasteful number, since it uses less digits than its factorization.

21000431243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173557305 (or 173557294 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

Adding to 21000431243 its reverse (34213400012), we get a palindrome (55213831255).

The spelling of 21000431243 in words is "twenty-one billion, four hundred thirty-one thousand, two hundred forty-three".