21661015661113 has 4 divisors (see below), whose sum is σ = 21661520117248. Its totient is φ = 21660511204980.

The previous prime is 21661015661039. The next prime is 21661015661239. The reversal of 21661015661113 is 31116651016612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21661015661113 - 2¹⁷ = 21661015530041 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21661015667113) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 252163653 + ... + 252249538.

It is an arithmetic number, because the mean of its divisors is an integer number (5415380029312).

Almost surely, 2^{21661015661113} is an apocalyptic number.

It is an amenable number.

21661015661113 is a deficient number, since it is larger than the sum of its proper divisors (504456135).

21661015661113 is an equidigital number, since it uses as much as digits as its factorization.

21661015661113 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 504456134.

The product of its (nonzero) digits is 38880, while the sum is 40.

Adding to 21661015661113 its reverse (31116651016612), we get a palindrome (52777666677725).

The spelling of 21661015661113 in words is "twenty-one trillion, six hundred sixty-one billion, fifteen million, six hundred sixty-one thousand, one hundred thirteen".