21001066 has 4 divisors (see below), whose sum is σ = 31501602. Its totient is φ = 10500532.

The previous prime is 21001049. The next prime is 21001081. The reversal of 21001066 is 66010012.

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., 18533025 + 2468041 = 4305^2 + 1571^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250265 + ... + 5250268.

Almost surely, 2^21001066 is an apocalyptic number.

21001066 is a deficient number, since it is larger than the sum of its proper divisors (10500536).

21001066 is a wasteful number, since it uses less digits than its factorization.

21001066 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10500535.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21001066 is about 4582.6920036153. The cubic root of 21001066 is about 275.8970858340.

Adding to 21001066 its reverse (66010012), we get a palindrome (87011078).

The spelling of 21001066 in words is "twenty-one million, one thousand, sixty-six".