11506721557 has 4 divisors (see below), whose sum is σ = 11507367276. Its totient is φ = 11506075840.

The previous prime is 11506721521. The next prime is 11506721581. The reversal of 11506721557 is 75512760511.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4560165841 + 6946555716 = 67529^2 + 83346^2 .

It is a cyclic number.

It is not a de Polignac number, because 11506721557 - 2²³ = 11498332949 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (11506721357) 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, 295348 + ... + 332029.

It is an arithmetic number, because the mean of its divisors is an integer number (2876841819).

Almost surely, 2^11506721557 is an apocalyptic number.

It is an amenable number.

11506721557 is a deficient number, since it is larger than the sum of its proper divisors (645719).

11506721557 is an equidigital number, since it uses as much as digits as its factorization.

11506721557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645718.

The product of its (nonzero) digits is 73500, while the sum is 40.

The spelling of 11506721557 in words is "eleven billion, five hundred six million, seven hundred twenty-one thousand, five hundred fifty-seven".