21616121656601 has 4 divisors (see below), whose sum is σ = 21830142663204. Its totient is φ = 21402100650000.

The previous prime is 21616121656531. The next prime is 21616121656603. The reversal of 21616121656601 is 10665612161612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 20275667128201 + 1340454528400 = 4502851^2 + 1157780^2 .

It is a cyclic number.

It is not a de Polignac number, because 21616121656601 - 2¹⁰ = 21616121655577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21616121656603) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107010503150 + ... + 107010503351.

It is an arithmetic number, because the mean of its divisors is an integer number (5457535665801).

Almost surely, 2^{21616121656601} is an apocalyptic number.

It is an amenable number.

21616121656601 is a deficient number, since it is larger than the sum of its proper divisors (214021006603).

21616121656601 is a wasteful number, since it uses less digits than its factorization.

21616121656601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214021006602.

The product of its (nonzero) digits is 155520, while the sum is 44.

The spelling of 21616121656601 in words is "twenty-one trillion, six hundred sixteen billion, one hundred twenty-one million, six hundred fifty-six thousand, six hundred one".