21621660653 has 8 divisors (see below), whose sum is σ = 21956371200. Its totient is φ = 21288475728.

The previous prime is 21621660649. The next prime is 21621660661. The reversal of 21621660653 is 35606612612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21621660653 - 2² = 21621660649 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621600653) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 352826 + ... + 409547.

It is an arithmetic number, because the mean of its divisors is an integer number (2744546400).

Almost surely, 2^21621660653 is an apocalyptic number.

It is an amenable number.

21621660653 is a deficient number, since it is larger than the sum of its proper divisors (334710547).

21621660653 is an equidigital number, since it uses as much as digits as its factorization.

21621660653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 762811.

The product of its (nonzero) digits is 77760, while the sum is 38.

The spelling of 21621660653 in words is "twenty-one billion, six hundred twenty-one million, six hundred sixty thousand, six hundred fifty-three".