21643876801 has 4 divisors (see below), whose sum is σ = 21657815172. Its totient is φ = 21629938432.

The previous prime is 21643876789. The next prime is 21643876879. The reversal of 21643876801 is 10867834612.

It is a happy number.

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 1614834225 + 20029042576 = 40185^2 + 141524^2 .

It is a cyclic number.

It is not a de Polignac number, because 21643876801 - 2⁷ = 21643876673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21643876301) 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, 6966856 + ... + 6969961.

It is an arithmetic number, because the mean of its divisors is an integer number (5414453793).

Almost surely, 2^21643876801 is an apocalyptic number.

It is an amenable number.

21643876801 is a deficient number, since it is larger than the sum of its proper divisors (13938371).

21643876801 is a wasteful number, since it uses less digits than its factorization.

21643876801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13938370.

The product of its (nonzero) digits is 387072, while the sum is 46.

The spelling of 21643876801 in words is "twenty-one billion, six hundred forty-three million, eight hundred seventy-six thousand, eight hundred one".