21375567391 has 2 divisors, whose sum is σ = 21375567392. Its totient is φ = 21375567390.

The previous prime is 21375567377. The next prime is 21375567419. The reversal of 21375567391 is 19376557312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21375567391 - 2²⁹ = 20838696479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21375597391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10687783695 + 10687783696.

It is an arithmetic number, because the mean of its divisors is an integer number (10687783696).

Almost surely, 2^21375567391 is an apocalyptic number.

21375567391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21375567391 is an equidigital number, since it uses as much as digits as its factorization.

21375567391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1190700, while the sum is 49.

The spelling of 21375567391 in words is "twenty-one billion, three hundred seventy-five million, five hundred sixty-seven thousand, three hundred ninety-one".