12105721557 has 12 divisors (see below), whose sum is σ = 18050108544. Its totient is φ = 7810142760.

The previous prime is 12105721513. The next prime is 12105721559. The reversal of 12105721557 is 75512750121.

12105721557 is a `hidden beast` number, since 1 + 21 + 0 + 572 + 15 + 57 = 666.

It is not a de Polignac number, because 12105721557 - 2²⁰ = 12104672981 is a prime.

It is a super-2 number, since 2×12105721557² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12105721559) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21694563 + ... + 21695120.

It is an arithmetic number, because the mean of its divisors is an integer number (1504175712).

Almost surely, 2^12105721557 is an apocalyptic number.

It is an amenable number.

12105721557 is a deficient number, since it is larger than the sum of its proper divisors (5944386987).

12105721557 is a wasteful number, since it uses less digits than its factorization.

12105721557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43389720 (or 43389717 counting only the distinct ones).

The product of its (nonzero) digits is 24500, while the sum is 36.

The spelling of 12105721557 in words is "twelve billion, one hundred five million, seven hundred twenty-one thousand, five hundred fifty-seven".