15561621205503 has 4 divisors (see below), whose sum is σ = 20748828274008. Its totient is φ = 10374414137000.

The previous prime is 15561621205463. The next prime is 15561621205511. The reversal of 15561621205503 is 30550212616551.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 15561621205503 - 2¹² = 15561621201407 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15561621205523) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2593603534248 + ... + 2593603534253.

It is an arithmetic number, because the mean of its divisors is an integer number (5187207068502).

Almost surely, 2^{15561621205503} is an apocalyptic number.

15561621205503 is a deficient number, since it is larger than the sum of its proper divisors (5187207068505).

15561621205503 is an equidigital number, since it uses as much as digits as its factorization.

15561621205503 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5187207068504.

The product of its (nonzero) digits is 270000, while the sum is 42.

The spelling of 15561621205503 in words is "fifteen trillion, five hundred sixty-one billion, six hundred twenty-one million, two hundred five thousand, five hundred three".