20661145251311 has 4 divisors (see below), whose sum is σ = 20661328305000. Its totient is φ = 20660962197624.

The previous prime is 20661145251293. The next prime is 20661145251343. The reversal of 20661145251311 is 11315254116602.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20661145251311 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 (20661145251611) 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, 91357436 + ... + 91583313.

It is an arithmetic number, because the mean of its divisors is an integer number (5165332076250).

Almost surely, 2^{20661145251311} is an apocalyptic number.

20661145251311 is a deficient number, since it is larger than the sum of its proper divisors (183053689).

20661145251311 is a wasteful number, since it uses less digits than its factorization.

20661145251311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183053688.

The product of its (nonzero) digits is 43200, while the sum is 38.

Adding to 20661145251311 its reverse (11315254116602), we get a palindrome (31976399367913).

The spelling of 20661145251311 in words is "twenty trillion, six hundred sixty-one billion, one hundred forty-five million, two hundred fifty-one thousand, three hundred eleven".