21530817 has 24 divisors (see below), whose sum is σ = 38775360. Its totient is φ = 11184480.

The previous prime is 21530813. The next prime is 21530827. The reversal of 21530817 is 71803512.

It is not a de Polignac number, because 21530817 - 2² = 21530813 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21530813) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 14842 + ... + 16227.

It is an arithmetic number, because the mean of its divisors is an integer number (1615640).

Almost surely, 2^21530817 is an apocalyptic number.

It is an amenable number.

21530817 is a deficient number, since it is larger than the sum of its proper divisors (17244543).

21530817 is a wasteful number, since it uses less digits than its factorization.

21530817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31093 (or 31090 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 21530817 is about 4640.1311403882. The cubic root of 21530817 is about 278.1976795623.

The spelling of 21530817 in words is "twenty-one million, five hundred thirty thousand, eight hundred seventeen".