21865424690687 has 2 divisors, whose sum is σ = 21865424690688. Its totient is φ = 21865424690686.

The previous prime is 21865424690671. The next prime is 21865424690689. The reversal of 21865424690687 is 78609642456812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21865424690687 - 2⁴ = 21865424690671 is a prime.

Together with 21865424690689, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21865424690689) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932712345343 + 10932712345344.

It is an arithmetic number, because the mean of its divisors is an integer number (10932712345344).

Almost surely, 2^{21865424690687} is an apocalyptic number.

21865424690687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21865424690687 is an equidigital number, since it uses as much as digits as its factorization.

21865424690687 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 278691840, while the sum is 68.

The spelling of 21865424690687 in words is "twenty-one trillion, eight hundred sixty-five billion, four hundred twenty-four million, six hundred ninety thousand, six hundred eighty-seven".