21580891 has 2 divisors, whose sum is σ = 21580892. Its totient is φ = 21580890.

The previous prime is 21580873. The next prime is 21580907. The reversal of 21580891 is 19808512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21580891 - 2⁵ = 21580859 is a prime.

It is not a weakly prime, because it can be changed into another prime (21580841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10790445 + 10790446.

It is an arithmetic number, because the mean of its divisors is an integer number (10790446).

Almost surely, 2^21580891 is an apocalyptic number.

21580891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21580891 is an equidigital number, since it uses as much as digits as its factorization.

21580891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 21580891 is about 4645.5237594915. The cubic root of 21580891 is about 278.4131797486.

The spelling of 21580891 in words is "twenty-one million, five hundred eighty thousand, eight hundred ninety-one".