15655521621 has 4 divisors (see below), whose sum is σ = 20874028832. Its totient is φ = 10437014412.

The previous prime is 15655521613. The next prime is 15655521683. The reversal of 15655521621 is 12612555651.

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.

It is not a de Polignac number, because 15655521621 - 2³ = 15655521613 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 15655521621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15655521421) 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, 2609253601 + ... + 2609253606.

It is an arithmetic number, because the mean of its divisors is an integer number (5218507208).

Almost surely, 2^15655521621 is an apocalyptic number.

It is an amenable number.

15655521621 is a deficient number, since it is larger than the sum of its proper divisors (5218507211).

15655521621 is an equidigital number, since it uses as much as digits as its factorization.

15655521621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5218507210.

The product of its digits is 90000, while the sum is 39.

The spelling of 15655521621 in words is "fifteen billion, six hundred fifty-five million, five hundred twenty-one thousand, six hundred twenty-one".