21653412165 has 192 divisors, whose sum is σ = 48670502400. Its totient is φ = 8641382400.

The previous prime is 21653412163. The next prime is 21653412167. The reversal of 21653412165 is 56121435612.

21653412165 is a `hidden beast` number, since 21 + 65 + 3 + 412 + 165 = 666.

It is an interprime number because it is at equal distance from previous prime (21653412163) and next prime (21653412167).

It is not a de Polignac number, because 21653412165 - 2¹ = 21653412163 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21653412161) by changing a digit.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 23010595 + ... + 23011535.

It is an arithmetic number, because the mean of its divisors is an integer number (253492200).

Almost surely, 2^21653412165 is an apocalyptic number.

It is an amenable number.

21653412165 is an abundant number, since it is smaller than the sum of its proper divisors (27017090235).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21653412165 is a wasteful number, since it uses less digits than its factorization.

21653412165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1228 (or 1225 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

Adding to 21653412165 its reverse (56121435612), we get a palindrome (77774847777).

The spelling of 21653412165 in words is "twenty-one billion, six hundred fifty-three million, four hundred twelve thousand, one hundred sixty-five".