201665115561 has 64 divisors (see below), whose sum is σ = 336698449920. Its totient is φ = 104524611840.

The previous prime is 201665115557. The next prime is 201665115581. The reversal of 201665115561 is 165511566102.

It is not a de Polignac number, because 201665115561 - 2² = 201665115557 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (201665115551) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 18362770 + ... + 18373748.

It is an arithmetic number, because the mean of its divisors is an integer number (5260913280).

Almost surely, 2^201665115561 is an apocalyptic number.

201665115561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

201665115561 is a deficient number, since it is larger than the sum of its proper divisors (135033334359).

201665115561 is a wasteful number, since it uses less digits than its factorization.

201665115561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12166.

The product of its (nonzero) digits is 54000, while the sum is 39.

The spelling of 201665115561 in words is "two hundred one billion, six hundred sixty-five million, one hundred fifteen thousand, five hundred sixty-one".