1311231505021 has 4 divisors (see below), whose sum is σ = 1311237026044. Its totient is φ = 1311225984000.

The previous prime is 1311231504997. The next prime is 1311231505069. The reversal of 1311231505021 is 1205051321131.

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

It can be written as a sum of positive squares in 2 ways, for example, as 840650596900 + 470580908121 = 916870^2 + 685989^2 .

It is a cyclic number.

It is not a de Polignac number, because 1311231505021 - 2⁷ = 1311231504893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1311231505091) 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, 2387460 + ... + 2884861.

It is an arithmetic number, because the mean of its divisors is an integer number (327809256511).

Almost surely, 2^{1311231505021} is an apocalyptic number.

It is an amenable number.

1311231505021 is a deficient number, since it is larger than the sum of its proper divisors (5521023).

1311231505021 is an equidigital number, since it uses as much as digits as its factorization.

1311231505021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5521022.

The product of its (nonzero) digits is 900, while the sum is 25.

Adding to 1311231505021 its reverse (1205051321131), we get a palindrome (2516282826152).

The spelling of 1311231505021 in words is "one trillion, three hundred eleven billion, two hundred thirty-one million, five hundred five thousand, twenty-one".