21573691 has 2 divisors, whose sum is σ = 21573692. Its totient is φ = 21573690.

The previous prime is 21573679. The next prime is 21573707. The reversal of 21573691 is 19637512.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21573691 is a prime.

It is not a weakly prime, because it can be changed into another prime (21573191) 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, 10786845 + 10786846.

It is an arithmetic number, because the mean of its divisors is an integer number (10786846).

Almost surely, 2^21573691 is an apocalyptic number.

21573691 is a deficient number, since it is larger than the sum of its proper divisors (1).

21573691 is an equidigital number, since it uses as much as digits as its factorization.

21573691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11340, while the sum is 34.

The square root of 21573691 is about 4644.7487553150. The cubic root of 21573691 is about 278.3822141154.

The spelling of 21573691 in words is "twenty-one million, five hundred seventy-three thousand, six hundred ninety-one".