21655719847 has 2 divisors, whose sum is σ = 21655719848. Its totient is φ = 21655719846.

The previous prime is 21655719733. The next prime is 21655719893. The reversal of 21655719847 is 74891755612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21655719847 - 2¹⁹ = 21655195559 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21655716847) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827859923 + 10827859924.

It is an arithmetic number, because the mean of its divisors is an integer number (10827859924).

Almost surely, 2^21655719847 is an apocalyptic number.

21655719847 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655719847 is an equidigital number, since it uses as much as digits as its factorization.

21655719847 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4233600, while the sum is 55.

The spelling of 21655719847 in words is "twenty-one billion, six hundred fifty-five million, seven hundred nineteen thousand, eight hundred forty-seven".