21240131243 has 4 divisors (see below), whose sum is σ = 21243028800. Its totient is φ = 21237233688.

The previous prime is 21240131233. The next prime is 21240131261. The reversal of 21240131243 is 34213104212.

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 21240131243 - 2⁸ = 21240130987 is a prime.

It is a super-2 number, since 2×21240131243² (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 (21240131233) 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, 1437755 + ... + 1452452.

It is an arithmetic number, because the mean of its divisors is an integer number (5310757200).

Almost surely, 2^21240131243 is an apocalyptic number.

21240131243 is a deficient number, since it is larger than the sum of its proper divisors (2897557).

21240131243 is an equidigital number, since it uses as much as digits as its factorization.

21240131243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2897556.

The product of its (nonzero) digits is 1152, while the sum is 23.

Adding to 21240131243 its reverse (34213104212), we get a palindrome (55453235455).

The spelling of 21240131243 in words is "twenty-one billion, two hundred forty million, one hundred thirty-one thousand, two hundred forty-three".