11535666021561 has 16 divisors (see below), whose sum is σ = 17169363383040. Its totient is φ = 6828724071120.

The previous prime is 11535666021557. The next prime is 11535666021773. The reversal of 11535666021561 is 16512066653511.

It is a happy number.

It is not a de Polignac number, because 11535666021561 - 2² = 11535666021557 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 11535666021561.

It is not an unprimeable number, because it can be changed into a prime (11535666023561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4064715291 + ... + 4064718128.

It is an arithmetic number, because the mean of its divisors is an integer number (1073085211440).

Almost surely, 2^{11535666021561} is an apocalyptic number.

11535666021561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

11535666021561 is a deficient number, since it is larger than the sum of its proper divisors (5633697361479).

11535666021561 is a wasteful number, since it uses less digits than its factorization.

11535666021561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8129433476.

The product of its (nonzero) digits is 972000, while the sum is 48.

The spelling of 11535666021561 in words is "eleven trillion, five hundred thirty-five billion, six hundred sixty-six million, twenty-one thousand, five hundred sixty-one".