15625666561 has 4 divisors (see below), whose sum is σ = 16305043392. Its totient is φ = 14946289732.

The previous prime is 15625666549. The next prime is 15625666583. The reversal of 15625666561 is 16566652651.

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 15625666561 - 2¹¹ = 15625664513 is a prime.

It is a super-2 number, since 2×15625666561² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15625616561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 339688381 + ... + 339688426.

It is an arithmetic number, because the mean of its divisors is an integer number (4076260848).

Almost surely, 2^15625666561 is an apocalyptic number.

It is an amenable number.

15625666561 is a deficient number, since it is larger than the sum of its proper divisors (679376831).

15625666561 is an equidigital number, since it uses as much as digits as its factorization.

15625666561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 679376830.

The product of its digits is 1944000, while the sum is 49.

The spelling of 15625666561 in words is "fifteen billion, six hundred twenty-five million, six hundred sixty-six thousand, five hundred sixty-one".