21302917 has 4 divisors (see below), whose sum is σ = 21382380. Its totient is φ = 21223456.

The previous prime is 21302909. The next prime is 21302923. The reversal of 21302917 is 71920312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 3587236 + 17715681 = 1894^2 + 4209^2 .

It is a cyclic number.

It is not a de Polignac number, because 21302917 - 2³ = 21302909 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21302891 and 21302900.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21302927) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39328 + ... + 39865.

It is an arithmetic number, because the mean of its divisors is an integer number (5345595).

Almost surely, 2^21302917 is an apocalyptic number.

It is an amenable number.

21302917 is a deficient number, since it is larger than the sum of its proper divisors (79463).

21302917 is an equidigital number, since it uses as much as digits as its factorization.

21302917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79462.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 21302917 is about 4615.5083143680. The cubic root of 21302917 is about 277.2126376247.

The spelling of 21302917 in words is "twenty-one million, three hundred two thousand, nine hundred seventeen".