21122116505661 has 16 divisors (see below), whose sum is σ = 29085199891200. Its totient is φ = 13626954747648.

The previous prime is 21122116505599. The next prime is 21122116505683. The reversal of 21122116505661 is 16650561122112.

It is not a de Polignac number, because 21122116505661 - 2¹⁷ = 21122116374589 is a prime.

It is a super-2 number, since 2×21122116505661² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21122116505761) 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, 841573096 + ... + 841598193.

It is an arithmetic number, because the mean of its divisors is an integer number (1817824993200).

Almost surely, 2^{21122116505661} is an apocalyptic number.

It is an amenable number.

21122116505661 is a deficient number, since it is larger than the sum of its proper divisors (7963083385539).

21122116505661 is a wasteful number, since it uses less digits than its factorization.

21122116505661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1683171428.

The product of its (nonzero) digits is 43200, while the sum is 39.

Adding to 21122116505661 its reverse (16650561122112), we get a palindrome (37772677627773).

The spelling of 21122116505661 in words is "twenty-one trillion, one hundred twenty-two billion, one hundred sixteen million, five hundred five thousand, six hundred sixty-one".