21162506891 has 2 divisors, whose sum is σ = 21162506892. Its totient is φ = 21162506890.

The previous prime is 21162506881. The next prime is 21162506909. The reversal of 21162506891 is 19860526112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21162506891 - 2¹⁴ = 21162490507 is a prime.

It is not a weakly prime, because it can be changed into another prime (21162506881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10581253445 + 10581253446.

It is an arithmetic number, because the mean of its divisors is an integer number (10581253446).

Almost surely, 2^21162506891 is an apocalyptic number.

21162506891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21162506891 is an equidigital number, since it uses as much as digits as its factorization.

21162506891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 51840, while the sum is 41.

The spelling of 21162506891 in words is "twenty-one billion, one hundred sixty-two million, five hundred six thousand, eight hundred ninety-one".