21641882921 has 2 divisors, whose sum is σ = 21641882922. Its totient is φ = 21641882920.

The previous prime is 21641882917. The next prime is 21641882947. The reversal of 21641882921 is 12928814612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19055041600 + 2586841321 = 138040^2 + 50861^2 .

It is a cyclic number.

It is not a de Polignac number, because 21641882921 - 2² = 21641882917 is a prime.

It is not a weakly prime, because it can be changed into another prime (21641882971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10820941460 + 10820941461.

It is an arithmetic number, because the mean of its divisors is an integer number (10820941461).

Almost surely, 2^21641882921 is an apocalyptic number.

It is an amenable number.

21641882921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21641882921 is an equidigital number, since it uses as much as digits as its factorization.

21641882921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 110592, while the sum is 44.

The spelling of 21641882921 in words is "twenty-one billion, six hundred forty-one million, eight hundred eighty-two thousand, nine hundred twenty-one".