15559818121 has 3 divisors (see below), whose sum is σ = 15559942861. Its totient is φ = 15559693382.

The previous prime is 15559818107. The next prime is 15559818151. The reversal of 15559818121 is 12181895551.

The square root of 15559818121 is 124739.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 15559818121 - 2¹⁹ = 15559293833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15559818151) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 62370 + ... + 187108.

Almost surely, 2^15559818121 is an apocalyptic number.

15559818121 is the 124739-th square number.

15559818121 is the 62370-th centered octagonal number.

It is an amenable number.

15559818121 is a deficient number, since it is larger than the sum of its proper divisors (124740).

15559818121 is an frugal number, since it uses more digits than its factorization.

15559818121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249478 (or 124739 counting only the distinct ones).

The product of its digits is 144000, while the sum is 46.

The spelling of 15559818121 in words is "fifteen billion, five hundred fifty-nine million, eight hundred eighteen thousand, one hundred twenty-one".