21530671 has 2 divisors, whose sum is σ = 21530672. Its totient is φ = 21530670.

The previous prime is 21530669. The next prime is 21530701. The reversal of 21530671 is 17603512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21530671 - 2¹ = 21530669 is a prime.

Together with 21530669, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21530471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765335 + 10765336.

It is an arithmetic number, because the mean of its divisors is an integer number (10765336).

Almost surely, 2^21530671 is an apocalyptic number.

21530671 is a deficient number, since it is larger than the sum of its proper divisors (1).

21530671 is an equidigital number, since it uses as much as digits as its factorization.

21530671 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21530671 is about 4640.1154080475. The cubic root of 21530671 is about 278.1970507434.

It can be divided in two parts, 21530 and 671, that added together give a square (22201 = 149²).

The spelling of 21530671 in words is "twenty-one million, five hundred thirty thousand, six hundred seventy-one".