21286691 has 2 divisors, whose sum is σ = 21286692. Its totient is φ = 21286690.

The previous prime is 21286673. The next prime is 21286693. The reversal of 21286691 is 19668212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21286691 - 2⁶ = 21286627 is a prime.

It is a Sophie Germain prime.

Together with 21286693, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21286693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10643345 + 10643346.

It is an arithmetic number, because the mean of its divisors is an integer number (10643346).

Almost surely, 2^21286691 is an apocalyptic number.

21286691 is a deficient number, since it is larger than the sum of its proper divisors (1).

21286691 is an equidigital number, since it uses as much as digits as its factorization.

21286691 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 35.

The square root of 21286691 is about 4613.7502099702. The cubic root of 21286691 is about 277.1422373322.

The spelling of 21286691 in words is "twenty-one million, two hundred eighty-six thousand, six hundred ninety-one".