21080817 has 20 divisors (see below), whose sum is σ = 31628916. Its totient is φ = 13992480.

The previous prime is 21080797. The next prime is 21080831. The reversal of 21080817 is 71808012.

It can be written as a sum of positive squares in 2 ways, for example, as 3111696 + 17969121 = 1764^2 + 4239^2 .

It is not a de Polignac number, because 21080817 - 2⁶ = 21080753 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21080887) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 25267 + ... + 26087.

Almost surely, 2^21080817 is an apocalyptic number.

21080817 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21080817 is a deficient number, since it is larger than the sum of its proper divisors (10548099).

21080817 is an equidigital number, since it uses as much as digits as its factorization.

21080817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1150 (or 1141 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 21080817 is about 4591.3850851350. The cubic root of 21080817 is about 276.2458820186.

Adding to 21080817 its reverse (71808012), we get a palindrome (92888829).

The spelling of 21080817 in words is "twenty-one million, eighty thousand, eight hundred seventeen".