21151718639 has 2 divisors, whose sum is σ = 21151718640. Its totient is φ = 21151718638.

The previous prime is 21151718617. The next prime is 21151718647. The reversal of 21151718639 is 93681715112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21151718639 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21151718639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21151718039) 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, 10575859319 + 10575859320.

It is an arithmetic number, because the mean of its divisors is an integer number (10575859320).

Almost surely, 2^21151718639 is an apocalyptic number.

21151718639 is a deficient number, since it is larger than the sum of its proper divisors (1).

21151718639 is an equidigital number, since it uses as much as digits as its factorization.

21151718639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 90720, while the sum is 44.

The spelling of 21151718639 in words is "twenty-one billion, one hundred fifty-one million, seven hundred eighteen thousand, six hundred thirty-nine".