15551121521 has 8 divisors (see below), whose sum is σ = 16748362344. Its totient is φ = 14354023680.

The previous prime is 15551121503. The next prime is 15551121581. The reversal of 15551121521 is 12512115551.

It can be written as a sum of positive squares in 4 ways, for example, as 91680625 + 15459440896 = 9575^2 + 124336^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15551121521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15551121581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 325211 + ... + 369951.

It is an arithmetic number, because the mean of its divisors is an integer number (2093545293).

Almost surely, 2^15551121521 is an apocalyptic number.

It is an amenable number.

15551121521 is a deficient number, since it is larger than the sum of its proper divisors (1197240823).

15551121521 is a wasteful number, since it uses less digits than its factorization.

15551121521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71491.

The product of its digits is 2500, while the sum is 29.

The spelling of 15551121521 in words is "fifteen billion, five hundred fifty-one million, one hundred twenty-one thousand, five hundred twenty-one".