1213120021 has 6 divisors (see below), whose sum is σ = 1236443810. Its totient is φ = 1190228208.

The previous prime is 1213119991. The next prime is 1213120039. The reversal of 1213120021 is 1200213121.

It can be written as a sum of positive squares in 3 ways, for example, as 534256996 + 678863025 = 23114^2 + 26055^2 .

It is not a de Polignac number, because 1213120021 - 2²⁹ = 676249109 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1213119983 and 1213120010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1213120081) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 213126 + ... + 218743.

Almost surely, 2^1213120021 is an apocalyptic number.

It is an amenable number.

1213120021 is a deficient number, since it is larger than the sum of its proper divisors (23323789).

1213120021 is an frugal number, since it uses more digits than its factorization.

1213120021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 431975 (or 431922 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 13.

The square root of 1213120021 is about 34829.8725378087. The cubic root of 1213120021 is about 1066.5173463614.

Adding to 1213120021 its reverse (1200213121), we get a palindrome (2413333142).

The spelling of 1213120021 in words is "one billion, two hundred thirteen million, one hundred twenty thousand, twenty-one".