21956378159 has 2 divisors, whose sum is σ = 21956378160. Its totient is φ = 21956378158.

The previous prime is 21956378117. The next prime is 21956378161. The reversal of 21956378159 is 95187365912.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21956378159 is a prime.

It is a super-2 number, since 2×21956378159² (a number of 21 digits) contains 22 as substring.

Together with 21956378161, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21956378189) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10978189079 + 10978189080.

It is an arithmetic number, because the mean of its divisors is an integer number (10978189080).

Almost surely, 2^21956378159 is an apocalyptic number.

21956378159 is a deficient number, since it is larger than the sum of its proper divisors (1).

21956378159 is an equidigital number, since it uses as much as digits as its factorization.

21956378159 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4082400, while the sum is 56.

The spelling of 21956378159 in words is "twenty-one billion, nine hundred fifty-six million, three hundred seventy-eight thousand, one hundred fifty-nine".