1555404121 has 4 divisors (see below), whose sum is σ = 1555484112. Its totient is φ = 1555324132.

The previous prime is 1555404077. The next prime is 1555404131. The reversal of 1555404121 is 1214045551.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1555404121 - 2⁹ = 1555403609 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1555404121.

It is not an unprimeable number, because it can be changed into a prime (1555404131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10026 + ... + 56668.

It is an arithmetic number, because the mean of its divisors is an integer number (388871028).

Almost surely, 2^1555404121 is an apocalyptic number.

It is an amenable number.

1555404121 is a deficient number, since it is larger than the sum of its proper divisors (79991).

1555404121 is an equidigital number, since it uses as much as digits as its factorization.

1555404121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79990.

The product of its (nonzero) digits is 4000, while the sum is 28.

The square root of 1555404121 is about 39438.6120572213. The cubic root of 1555404121 is about 1158.6379477503.

Adding to 1555404121 its reverse (1214045551), we get a palindrome (2769449672).

The spelling of 1555404121 in words is "one billion, five hundred fifty-five million, four hundred four thousand, one hundred twenty-one".