21530066 has 4 divisors (see below), whose sum is σ = 32295102. Its totient is φ = 10765032.

The previous prime is 21530017. The next prime is 21530077. The reversal of 21530066 is 66003512.

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

It can be written as a sum of positive squares in only one way, i.e., 12355225 + 9174841 = 3515^2 + 3029^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5382515 + ... + 5382518.

Almost surely, 2^21530066 is an apocalyptic number.

21530066 is a deficient number, since it is larger than the sum of its proper divisors (10765036).

21530066 is a wasteful number, since it uses less digits than its factorization.

21530066 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10765035.

The product of its (nonzero) digits is 1080, while the sum is 23.

The square root of 21530066 is about 4640.0502152455. The cubic root of 21530066 is about 278.1944449910.

Adding to 21530066 its reverse (66003512), we get a palindrome (87533578).

The spelling of 21530066 in words is "twenty-one million, five hundred thirty thousand, sixty-six".