21708766091 has 2 divisors, whose sum is σ = 21708766092. Its totient is φ = 21708766090.

The previous prime is 21708766067. The next prime is 21708766153. The reversal of 21708766091 is 19066780712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21708766091 - 2¹⁴ = 21708749707 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (21708766021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10854383045 + 10854383046.

It is an arithmetic number, because the mean of its divisors is an integer number (10854383046).

Almost surely, 2^21708766091 is an apocalyptic number.

21708766091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21708766091 is an equidigital number, since it uses as much as digits as its factorization.

21708766091 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 254016, while the sum is 47.

The spelling of 21708766091 in words is "twenty-one billion, seven hundred eight million, seven hundred sixty-six thousand, ninety-one".