1216021013 has 4 divisors (see below), whose sum is σ = 1217408460. Its totient is φ = 1214633568.

The previous prime is 1216020997. The next prime is 1216021019. The reversal of 1216021013 is 3101206121.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3101206121 = 13 ⋅238554317.

It can be written as a sum of positive squares in 2 ways, for example, as 426298609 + 789722404 = 20647^2 + 28102^2 .

It is a cyclic number.

It is not a de Polignac number, because 1216021013 - 2⁴ = 1216020997 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1216020982 and 1216021000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216021019) 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, 692408 + ... + 694161.

It is an arithmetic number, because the mean of its divisors is an integer number (304352115).

Almost surely, 2^1216021013 is an apocalyptic number.

It is an amenable number.

1216021013 is a deficient number, since it is larger than the sum of its proper divisors (1387447).

1216021013 is an equidigital number, since it uses as much as digits as its factorization.

1216021013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1387446.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 1216021013 is about 34871.4928415748. The cubic root of 1216021013 is about 1067.3668076029.

Adding to 1216021013 its reverse (3101206121), we get a palindrome (4317227134).

The spelling of 1216021013 in words is "one billion, two hundred sixteen million, twenty-one thousand, thirteen".