21956378189 has 2 divisors, whose sum is σ = 21956378190. Its totient is φ = 21956378188.

The previous prime is 21956378167. The next prime is 21956378209. The reversal of 21956378189 is 98187365912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13429333225 + 8527044964 = 115885^2 + 92342^2 .

It is a cyclic number.

It is not a de Polignac number, because 21956378189 - 2²⁴ = 21939600973 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21956378159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10978189094 + 10978189095.

It is an arithmetic number, because the mean of its divisors is an integer number (10978189095).

Almost surely, 2^21956378189 is an apocalyptic number.

It is an amenable number.

21956378189 is a deficient number, since it is larger than the sum of its proper divisors (1).

21956378189 is an equidigital number, since it uses as much as digits as its factorization.

21956378189 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6531840, while the sum is 59.

The spelling of 21956378189 in words is "twenty-one billion, nine hundred fifty-six million, three hundred seventy-eight thousand, one hundred eighty-nine".