21642601653 has 20 divisors (see below), whose sum is σ = 33118855308. Its totient is φ = 14076486720.

The previous prime is 21642601619. The next prime is 21642601699. The reversal of 21642601653 is 35610624612.

21642601653 is a `hidden beast` number, since 2 + 1 + 6 + 42 + 601 + 6 + 5 + 3 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 6799321764 + 14843279889 = 82458^2 + 121833^2 .

It is not a de Polignac number, because 21642601653 - 2²⁶ = 21575492789 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 (21642601153) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3255126 + ... + 3261767.

Almost surely, 2^21642601653 is an apocalyptic number.

It is an amenable number.

21642601653 is a deficient number, since it is larger than the sum of its proper divisors (11476253655).

21642601653 is an equidigital number, since it uses as much as digits as its factorization.

21642601653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6516946 (or 6516937 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The spelling of 21642601653 in words is "twenty-one billion, six hundred forty-two million, six hundred one thousand, six hundred fifty-three".