21807691 has 2 divisors, whose sum is σ = 21807692. Its totient is φ = 21807690.

The previous prime is 21807679. The next prime is 21807707. The reversal of 21807691 is 19670812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21807691 - 2⁵ = 21807659 is a prime.

It is not a weakly prime, because it can be changed into another prime (21807791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10903845 + 10903846.

It is an arithmetic number, because the mean of its divisors is an integer number (10903846).

Almost surely, 2^21807691 is an apocalyptic number.

21807691 is a deficient number, since it is larger than the sum of its proper divisors (1).

21807691 is an equidigital number, since it uses as much as digits as its factorization.

21807691 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 21807691 is about 4669.8705549512. The cubic root of 21807691 is about 279.3850919152.

The spelling of 21807691 in words is "twenty-one million, eight hundred seven thousand, six hundred ninety-one".