21956378287 has 2 divisors, whose sum is σ = 21956378288. Its totient is φ = 21956378286.

The previous prime is 21956378233. The next prime is 21956378293. The reversal of 21956378287 is 78287365912.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21956378287 - 2⁷ = 21956378159 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21956378387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10978189143 + 10978189144.

It is an arithmetic number, because the mean of its divisors is an integer number (10978189144).

Almost surely, 2^21956378287 is an apocalyptic number.

21956378287 is a deficient number, since it is larger than the sum of its proper divisors (1).

21956378287 is an equidigital number, since it uses as much as digits as its factorization.

21956378287 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10160640, while the sum is 58.

The spelling of 21956378287 in words is "twenty-one billion, nine hundred fifty-six million, three hundred seventy-eight thousand, two hundred eighty-seven".