21317552647 has 2 divisors, whose sum is σ = 21317552648. Its totient is φ = 21317552646.

The previous prime is 21317552563. The next prime is 21317552651. The reversal of 21317552647 is 74625571312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21317552647 - 2⁷ = 21317552519 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21317552147) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10658776323 + 10658776324.

It is an arithmetic number, because the mean of its divisors is an integer number (10658776324).

Almost surely, 2^21317552647 is an apocalyptic number.

21317552647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21317552647 is an equidigital number, since it uses as much as digits as its factorization.

21317552647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 352800, while the sum is 43.

The spelling of 21317552647 in words is "twenty-one billion, three hundred seventeen million, five hundred fifty-two thousand, six hundred forty-seven".