21355571791 has 2 divisors, whose sum is σ = 21355571792. Its totient is φ = 21355571790.

The previous prime is 21355571789. The next prime is 21355571807. The reversal of 21355571791 is 19717555312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21355571791 - 2¹ = 21355571789 is a prime.

Together with 21355571789, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21355571891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10677785895 + 10677785896.

It is an arithmetic number, because the mean of its divisors is an integer number (10677785896).

Almost surely, 2^21355571791 is an apocalyptic number.

21355571791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21355571791 is an equidigital number, since it uses as much as digits as its factorization.

21355571791 is an evil number, because the sum of its binary digits is even.

The product of its digits is 330750, while the sum is 46.

The spelling of 21355571791 in words is "twenty-one billion, three hundred fifty-five million, five hundred seventy-one thousand, seven hundred ninety-one".