21151718647 has 2 divisors, whose sum is σ = 21151718648. Its totient is φ = 21151718646.

The previous prime is 21151718639. The next prime is 21151718723. The reversal of 21151718647 is 74681715112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21151718647 - 2³ = 21151718639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21151718617) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10575859323 + 10575859324.

It is an arithmetic number, because the mean of its divisors is an integer number (10575859324).

Almost surely, 2^21151718647 is an apocalyptic number.

21151718647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21151718647 is an equidigital number, since it uses as much as digits as its factorization.

21151718647 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 94080, while the sum is 43.

The spelling of 21151718647 in words is "twenty-one billion, one hundred fifty-one million, seven hundred eighteen thousand, six hundred forty-seven".