1215780121 has 2 divisors, whose sum is σ = 1215780122. Its totient is φ = 1215780120.

The previous prime is 1215780061. The next prime is 1215780133. The reversal of 1215780121 is 1210875121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1115560000 + 100220121 = 33400^2 + 10011^2 .

It is a cyclic number.

It is not a de Polignac number, because 1215780121 - 2¹¹ = 1215778073 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1215780121.

It is not a weakly prime, because it can be changed into another prime (1215789121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 607890060 + 607890061.

It is an arithmetic number, because the mean of its divisors is an integer number (607890061).

Almost surely, 2^1215780121 is an apocalyptic number.

It is an amenable number.

1215780121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1215780121 is an equidigital number, since it uses as much as digits as its factorization.

1215780121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 28.

The square root of 1215780121 is about 34868.0386744078. The cubic root of 1215780121 is about 1067.2963216759.

The spelling of 1215780121 in words is "one billion, two hundred fifteen million, seven hundred eighty thousand, one hundred twenty-one".