1312051721 has 12 divisors (see below), whose sum is σ = 1452268692. Its totient is φ = 1181174016.

The previous prime is 1312051691. The next prime is 1312051777. The reversal of 1312051721 is 1271502131.

It can be written as a sum of positive squares in 2 ways, for example, as 736579600 + 575472121 = 27140^2 + 23989^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1312051721 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1312051021) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 63956 + ... + 81941.

It is an arithmetic number, because the mean of its divisors is an integer number (121022391).

Almost surely, 2^1312051721 is an apocalyptic number.

It is an amenable number.

1312051721 is a deficient number, since it is larger than the sum of its proper divisors (140216971).

1312051721 is a wasteful number, since it uses less digits than its factorization.

1312051721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145960 (or 145937 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 1312051721 is about 36222.2544991335. The cubic root of 1312051721 is about 1094.7551202091.

Adding to 1312051721 its reverse (1271502131), we get a palindrome (2583553852).

The spelling of 1312051721 in words is "one billion, three hundred twelve million, fifty-one thousand, seven hundred twenty-one".