21688561006507 has 2 divisors, whose sum is σ = 21688561006508. Its totient is φ = 21688561006506.

The previous prime is 21688561006477. The next prime is 21688561006513. The reversal of 21688561006507 is 70560016588612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21688561006507 - 2⁷ = 21688561006379 is a prime.

It is not a weakly prime, because it can be changed into another prime (21688561006597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10844280503253 + 10844280503254.

It is an arithmetic number, because the mean of its divisors is an integer number (10844280503254).

Almost surely, 2^{21688561006507} is an apocalyptic number.

21688561006507 is a deficient number, since it is larger than the sum of its proper divisors (1).

21688561006507 is an equidigital number, since it uses as much as digits as its factorization.

21688561006507 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4838400, while the sum is 55.

The spelling of 21688561006507 in words is "twenty-one trillion, six hundred eighty-eight billion, five hundred sixty-one million, six thousand, five hundred seven".