21943681957 has 8 divisors (see below), whose sum is σ = 23404084056. Its totient is φ = 20502124032.

The previous prime is 21943681943. The next prime is 21943681961. The reversal of 21943681957 is 75918634912.

It is a happy number.

It is a Cunningham number, because it is equal to 148134²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 12889969156 + 9053712801 = 113534^2 + 95151^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21943681957 - 2¹¹ = 21943679909 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21943681898 and 21943681907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21943688957) 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 in 7 ways as a sum of consecutive naturals, for example, 4708638 + ... + 4713295.

It is an arithmetic number, because the mean of its divisors is an integer number (2925510507).

Almost surely, 2^21943681957 is an apocalyptic number.

It is an amenable number.

21943681957 is a deficient number, since it is larger than the sum of its proper divisors (1460402099).

21943681957 is a wasteful number, since it uses less digits than its factorization.

21943681957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9422087.

The product of its digits is 3265920, while the sum is 55.

The spelling of 21943681957 in words is "twenty-one billion, nine hundred forty-three million, six hundred eighty-one thousand, nine hundred fifty-seven".