21164663645 has 4 divisors (see below), whose sum is σ = 25397596380. Its totient is φ = 16931730912.

The previous prime is 21164663633. The next prime is 21164663647. The reversal of 21164663645 is 54636646112.

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 11518870276 + 9645793369 = 107326^2 + 98213^2 .

It is a cyclic number.

It is not a de Polignac number, because 21164663645 - 2⁶ = 21164663581 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21164663596 and 21164663605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21164663647) 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, 2116466360 + ... + 2116466369.

It is an arithmetic number, because the mean of its divisors is an integer number (6349399095).

Almost surely, 2^21164663645 is an apocalyptic number.

It is an amenable number.

21164663645 is a deficient number, since it is larger than the sum of its proper divisors (4232932735).

21164663645 is an equidigital number, since it uses as much as digits as its factorization.

21164663645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4232932734.

The product of its digits is 622080, while the sum is 44.

The spelling of 21164663645 in words is "twenty-one billion, one hundred sixty-four million, six hundred sixty-three thousand, six hundred forty-five".