1312240021 has 4 divisors (see below), whose sum is σ = 1313617932. Its totient is φ = 1310862112.

The previous prime is 1312240009. The next prime is 1312240031. The reversal of 1312240021 is 1200422131.

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 805764996 + 506475025 = 28386^2 + 22505^2 .

It is a cyclic number.

It is not a de Polignac number, because 1312240021 - 2⁷ = 1312239893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1312239977 and 1312240004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1312240001) 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, 687526 + ... + 689431.

It is an arithmetic number, because the mean of its divisors is an integer number (328404483).

Almost surely, 2^1312240021 is an apocalyptic number.

It is an amenable number.

1312240021 is a deficient number, since it is larger than the sum of its proper divisors (1377911).

1312240021 is an equidigital number, since it uses as much as digits as its factorization.

1312240021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1377910.

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 1312240021 is about 36224.8536366953. The cubic root of 1312240021 is about 1094.8074892138.

Adding to 1312240021 its reverse (1200422131), we get a palindrome (2512662152).

The spelling of 1312240021 in words is "one billion, three hundred twelve million, two hundred forty thousand, twenty-one".