21398839687 has 2 divisors, whose sum is σ = 21398839688. Its totient is φ = 21398839686.

The previous prime is 21398839673. The next prime is 21398839691. The reversal of 21398839687 is 78693889312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21398839687 - 2⁷ = 21398839559 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21398839487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699419843 + 10699419844.

It is an arithmetic number, because the mean of its divisors is an integer number (10699419844).

Almost surely, 2^21398839687 is an apocalyptic number.

21398839687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398839687 is an equidigital number, since it uses as much as digits as its factorization.

21398839687 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31352832, while the sum is 64.

The spelling of 21398839687 in words is "twenty-one billion, three hundred ninety-eight million, eight hundred thirty-nine thousand, six hundred eighty-seven".