21081073 has 4 divisors (see below), whose sum is σ = 22702708. Its totient is φ = 19459440.

The previous prime is 21081061. The next prime is 21081101. The reversal of 21081073 is 37018012.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3717184 + 17363889 = 1928^2 + 4167^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21081073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21081043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 810798 + ... + 810823.

It is an arithmetic number, because the mean of its divisors is an integer number (5675677).

Almost surely, 2^21081073 is an apocalyptic number.

It is an amenable number.

21081073 is a deficient number, since it is larger than the sum of its proper divisors (1621635).

21081073 is a wasteful number, since it uses less digits than its factorization.

21081073 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1621634.

The product of its (nonzero) digits is 336, while the sum is 22.

The square root of 21081073 is about 4591.4129633480. The cubic root of 21081073 is about 276.2470002336.

Adding to 21081073 its reverse (37018012), we get a palindrome (58099085).

The spelling of 21081073 in words is "twenty-one million, eighty-one thousand, seventy-three".