21580817 has 2 divisors, whose sum is σ = 21580818. Its totient is φ = 21580816.

The previous prime is 21580813. The next prime is 21580841. The reversal of 21580817 is 71808512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13957696 + 7623121 = 3736^2 + 2761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21580817 - 2² = 21580813 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21580813) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10790408 + 10790409.

It is an arithmetic number, because the mean of its divisors is an integer number (10790409).

Almost surely, 2^21580817 is an apocalyptic number.

It is an amenable number.

21580817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21580817 is an equidigital number, since it uses as much as digits as its factorization.

21580817 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21580817 is about 4645.5157948284. The cubic root of 21580817 is about 278.4128615257.

The spelling of 21580817 in words is "twenty-one million, five hundred eighty thousand, eight hundred seventeen".