21897582491 has 2 divisors, whose sum is σ = 21897582492. Its totient is φ = 21897582490.

The previous prime is 21897582439. The next prime is 21897582493. The reversal of 21897582491 is 19428579812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21897582491 - 2³⁴ = 4717713307 is a prime.

Together with 21897582493, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21897582493) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10948791245 + 10948791246.

It is an arithmetic number, because the mean of its divisors is an integer number (10948791246).

Almost surely, 2^21897582491 is an apocalyptic number.

21897582491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21897582491 is an equidigital number, since it uses as much as digits as its factorization.

21897582491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2903040, while the sum is 56.

The spelling of 21897582491 in words is "twenty-one billion, eight hundred ninety-seven million, five hundred eighty-two thousand, four hundred ninety-one".