21684718087 has 2 divisors, whose sum is σ = 21684718088. Its totient is φ = 21684718086.

The previous prime is 21684718051. The next prime is 21684718141. The reversal of 21684718087 is 78081748612.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21684718087 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21684713087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10842359043 + 10842359044.

It is an arithmetic number, because the mean of its divisors is an integer number (10842359044).

Almost surely, 2^21684718087 is an apocalyptic number.

21684718087 is a deficient number, since it is larger than the sum of its proper divisors (1).

21684718087 is an equidigital number, since it uses as much as digits as its factorization.

21684718087 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1204224, while the sum is 52.

The spelling of 21684718087 in words is "twenty-one billion, six hundred eighty-four million, seven hundred eighteen thousand, eighty-seven".