21530071 has 4 divisors (see below), whose sum is σ = 21549312. Its totient is φ = 21510832.

The previous prime is 21530017. The next prime is 21530077. The reversal of 21530071 is 17003512.

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

It is a cyclic number.

It is not a de Polignac number, because 21530071 - 2¹⁷ = 21398999 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21530077) 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, 7831 + ... + 10216.

It is an arithmetic number, because the mean of its divisors is an integer number (5387328).

Almost surely, 2^21530071 is an apocalyptic number.

21530071 is a deficient number, since it is larger than the sum of its proper divisors (19241).

21530071 is a wasteful number, since it uses less digits than its factorization.

21530071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19240.

The product of its (nonzero) digits is 210, while the sum is 19.

The square root of 21530071 is about 4640.0507540328. The cubic root of 21530071 is about 278.1944665264.

Adding to 21530071 its reverse (17003512), we get a palindrome (38533583).

The spelling of 21530071 in words is "twenty-one million, five hundred thirty thousand, seventy-one".