815550121 has 2 divisors, whose sum is σ = 815550122. Its totient is φ = 815550120.

The previous prime is 815550079. The next prime is 815550137. The reversal of 815550121 is 121055518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 758396521 + 57153600 = 27539^2 + 7560^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-815550121 is a prime.

It is a super-2 number, since 2×815550121² = 1330243999726229282, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 815550121.

It is not a weakly prime, because it can be changed into another prime (815550161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 407775060 + 407775061.

It is an arithmetic number, because the mean of its divisors is an integer number (407775061).

Almost surely, 2^815550121 is an apocalyptic number.

It is an amenable number.

815550121 is a deficient number, since it is larger than the sum of its proper divisors (1).

815550121 is an equidigital number, since it uses as much as digits as its factorization.

815550121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2000, while the sum is 28.

The square root of 815550121 is about 28557.8381709821. The cubic root of 815550121 is about 934.2939834991.

The spelling of 815550121 in words is "eight hundred fifteen million, five hundred fifty thousand, one hundred twenty-one".