21654287491 has 2 divisors, whose sum is σ = 21654287492. Its totient is φ = 21654287490.

The previous prime is 21654287453. The next prime is 21654287513. The reversal of 21654287491 is 19478245612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21654287491 - 2²⁷ = 21520069763 is a prime.

It is not a weakly prime, because it can be changed into another prime (21654087491) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827143745 + 10827143746.

It is an arithmetic number, because the mean of its divisors is an integer number (10827143746).

Almost surely, 2^21654287491 is an apocalyptic number.

21654287491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21654287491 is an equidigital number, since it uses as much as digits as its factorization.

21654287491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 967680, while the sum is 49.

The spelling of 21654287491 in words is "twenty-one billion, six hundred fifty-four million, two hundred eighty-seven thousand, four hundred ninety-one".