21943681961 has 2 divisors, whose sum is σ = 21943681962. Its totient is φ = 21943681960.

The previous prime is 21943681943. The next prime is 21943681973. The reversal of 21943681961 is 16918634912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16880505625 + 5063176336 = 129925^2 + 71156^2 .

It is a cyclic number.

It is not a de Polignac number, because 21943681961 - 2⁶ = 21943681897 is a prime.

It is not a weakly prime, because it can be changed into another prime (21943681901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971840980 + 10971840981.

It is an arithmetic number, because the mean of its divisors is an integer number (10971840981).

Almost surely, 2^21943681961 is an apocalyptic number.

It is an amenable number.

21943681961 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943681961 is an equidigital number, since it uses as much as digits as its factorization.

21943681961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 559872, while the sum is 50.

The spelling of 21943681961 in words is "twenty-one billion, nine hundred forty-three million, six hundred eighty-one thousand, nine hundred sixty-one".